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LABORATORY EXERCISES 



"THE FIRST YEAR OF SCIENCE 



BY 

JOHN C. HESSLER, Ph. D. 

PROFESSOR OF CHEMISTRY, THE JAMES MILLIKIN UNIVERSITY 

LATE INSTRUCTOR IN THE UNIVERSITY OF CHICAGO AND 

IN THE HYDE PARK HIGH SCHOOL, CHICAGO 



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BENJ. H. SANBORN & CO. 

CHICAGO NEW YORK BOSTON 

1915 



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COPYRIGHT, 1915 

BY 

JOHN C. HESSLER 



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R. R. DONNELLEY r SONS COMPANY 
CHICAGO 



CONTENTS 

LABORATORY EXERCISES 

EXERCISE PAGE 

1 . Air Takes Up Room 1 

2. How to Measure Length and Area 3 

3. The Measuring of Volume and Capacity 4 

4. How to Weigh 5 

5. Plumb Line and Pendulum 7 

6. Inertia and Centrifugal Force 9 

7. Adhesion of Liquids to Solids; Liquid Surfaces 10 

8. Capillary Action 12 

9. Density 13 

10. Weight of a Stone in Air and in Water 14 

1 1 . Center of Mass 15 

12. Pressure of the Atmosphere 16 

13. Pressure of Water and of Air 17 

14. Collecting a Gas Over Water 18 

15. Substances Produced in Breathing and Burning 19 

16. Heating of Tin in Air 20 

17. Preparing Oxygen 21 

18. Air Dissolves in Water , 22 

19. Nitrogen; the Composition of Air 23 

20. Expansion and Contraction of Water 24 

21. Expansion and Contraction of Air 25 

22. Melting Point and Freezing Point; A Freezing Mixture. ... 26 

23. Boiling Points of Water and Alcohol 27 

24. Conduction of Heat 27 

25. Convection 28 

26. Is Heat Used Up When a Liquid is Changed to a Gas? 29 

27. Kindling Temperature 30 

28. Mixing Materials of Different Temperatures 30 

29. Contents of Natural Water 31 

iii 



iv CONTENTS 

EXERCISE PAGE 

30. Water Tests 32 

31. Filtering and Precipitating ; 33 

32. Crystals 34 

33. Does the Temperature Change During Solution? 35 

34. Hydrogen 35 

35. Hydrochloric Acid and Ammonia Water 36 

36. Chlorine 37 

37. Sulphur 38 

38. Charring of Carbon Compounds 39 

39. How Ores are Reduced to Metals 40 

40. Carbon Dioxide and Fermentation 41 

41. Lime 42 

42. Magnets 43 

43. Electric Charges 44 

44. A Simple Electric Cell 45 

45. The Sal Ammoniac Cell 46 

46. Electromagnets 47 

47. Shadows 48 

48. Brightness Changes with Distance 49 

49. Candle Power 50 

50. Mirrors 51 

51. Refraction of Light 52 

52. Of What is White Light Composed? 53 

53. How Color is Affected by the Kind of Light 55 

54. How Sound is Made and Carried 56 

55. How Sounds are Strengthened 57 

56. Levers 57 

57. Tools Based on the Lever 59 

58. Pulleys 60 

59. The Inclined Plane 61 

60. The Screw , 63 

61. Wheel and Axle 64 

62. Friction 65 

63. Applied Forms of Simple Machines 65 

64. Acids 66 

65. Bases, or Alkalies 67 



CONTENTS V 

EXERCISE PAGE 

66. Neutralizing a Base by an Acid 68 

67. Soap and Soap Making 69 

68. Testing of Cotton and Wool 70 

69. Dyeing 71 

70. Bleaching 73 

71. How to Remove Stains 74 

72. Plumbing 75 

73. Flames 76 

74. Gas and Electric Meters 78 

75. How Heating the Air Changes its Density 79 

76. The Dew Point 79 

77. Weather Records 80 

78. Weather Maps : 81 

79. Kinds of Rocks 81 

80. Concrete 82 

81. Ore Tests 83 

82. Kinds of Soil 86 

83. Soil Tests 86 

84> How Soils Take Up the Rain 87 

85. Contents of a Fertile Soil 89 

86. How Moisture is Taken Up by Plants 89 

87. Plants Give Off Moisture 91 

88. Seeds and Their Germination 92 

89. Materials Present in Plants 94 

90. Study of Leaves 96 

91. Stems 97 

92. Wood ; 99 

93. Roots 101 

94. The Flower. . 101 

95. The Earthworm 1Q3 

96. Mollusks 104 

97. Insects 105 

98. Birds , 107 

99. Bones and Joints 109 

100. Muscles and Tendons 110 

101. Foods and Food Tests . . Ill 



Vi CONTENTS 

EXERCISE PAGE 

102. The Mouth and Throat 112 

103. Digestion of Food 113 

104. The Blood Vessels 114 

105. Respiration 115 

106. The Nervous System 117 

107. The Eyes 117 



INTRODUCTION 

The laboratory exercises of the "First Year of Science" are, 
as the writer stated in the Preface to the text proper, such as 
can be performed with simple apparatus. To make the work 
of instruction easier, and to suggest substitutions of simpler 
forms of apparatus for those of the ordinary type, the following 
preliminary directions are given: 

1. An alcohol lamp (Exercise 73), a gasoline torch, or even 
a metal kerosene lamp with a metal chimney, may be used in 
place of a Bunsen gas burner. 

2. A ring stand can be made, if the laboratory has none 
(see Fig. 11, Exercise 16), out of telegraph wire and a wooden 
block. 

3. A test tube holder can be made by folding a strip of 
paper lengthwise. 

4. The only glass-working called for in these exercises is 
the bending of glass tubing. Tubing should be heated in a 
wing top or fish tail flame, if possible. An ordinary gas jet 
is excellent; so is the flame produced by a wide wick in a 
kerosene lamp. If an alcohol lamp must be used, the glass 
should be heated at one spot, then bent a little, then heated 
close by, and bent a little more, until a rounded bend is 
produced. If outspread flames are used, the glass should be 
held lengthwise with the flame. Sharp ends of tubing 
should be fire-polished, that is, the ends should be held in 
a flame until the glass just begins to melt. 

5. Pieces of thin sheet glass (squares about 4 inches on a 
side) do very well as substitutes for watch glasses, if they 
are laid in a horizontal position. 

vii 



Vlii INTRODUCTION 

6. Iron spoons ("tin" spoons) can be used for the heating 
of solids in the flame. 

7. A combustion spoon can be made out of a strip of "tin," 
about 54 of an inch wide, cut from a "tin" can. One end is 
rounded, and is bent up at right angles to the strip; the 
rounded end may be beaten into the shape of a shallow bowl. 

8. Measuring cups can be used instead of beakers, except 
when alkalies or acids are to be employed. 

9. Shot of two or three different sizes may be used instead 
of weights. If 100 of each size are weighed accurately, the 
student can take the average weight of each for his own 
weighings. The shot of each size should be kept in its own 
bottle, and the bottle should be properly labeled. 

10. "Mossy" tin for Exercise 19 may be made from bar 
tin. The tin should be melted, and poured into a pail of 
water. 

11. A "tin" test tube, for use in Exercise 37, may be made 
out of a strip about 3x5 inches cut from a "tin" can. 
The strip is rolled up into cylindrical form; then one end is 
pinched shut and turned upward. 

12. Generating bottles for gases (also the bottle for the 
"Diver," Exercise 13) may be made from glass fruit-jars 
with metal covers. Make a hole in the cover, fit to it a bent 
glass tube, and fasten the tube in place by means of a paste 
made out of "red lead" and glycerine. When the paste 
hardens, the jar is ready for use. If a rubber ring is used on 
the can, the cover can be screwed down air tight. 

13. For the color experiments (Exercises 52 and 53), the 
glazed paper used in kindergarten work is excellent. White 
paper may be colored by means of crayons, and used as a 
substitute. . 

14. Fehling's solution is often obtainable at a drug store. 
You can make a solution by dissolving 34.64 g. of copper 



INTRODUCTION IX 

sulphate in 500 cu. cm. of water; also 180 g. of Rochelle salt 
and 70 g. of sodium hydroxide in 500 cu. cm. of water. Mix 
equal volumes of the two solutions just before using. Of 
course any fractional part of this amount may be prepared. 

Part of the exercises of this manual have been gathered from 
existing sources; all have been simplified for the use of first-year 
students. The writer found many helpful suggestions for the 
exercises on "Soils" in a pamphlet entitled "Some Principles of 
Agriculture," presumably published by the Connecticut State 
Board of Education. 

J. C. H. 
Decatur, Illinois. 



LABOEATORY EXERCISES 



EXERCISE 1 
AIR TAKES UP ROOM 

Apparatus and Materials. Narrow-mouth bottle, water, thistle 
tube or funnel, wide-mouth bottle (about 250 cu.cm.), two-hole rubber 
stopper that fits the wide-mouth bottle, a glass plug or a round pencil, 
biscuit cutter, oil-can used for sewing machine (or a carpenter's oil- 
can), tin funnel. 

a. Fill a narrow-mouth bottle with water, and invert it over 
a sink or a jar. Tell how the water comes out of the bottle. 
Why does it not come out in a stream? 

6. Close the small end of the funnel or thistle tube tightly 
with your finger (Fig. 1), and put the 
large end into a deep pan or pail nearly 
filled with water. Does water enter? 
Remove your finger, and tell what 
happens. Tell why it happens. 

N. B. You can carry out this ex- 
periment with a piece of glass tubing 
open at both ends. 

c. Now put the stem of the funnel 
(or thistle tube) through one of the 
holes of the two-hole rubber stopper 
(Fig. 2). The glass slips through the 
rubber easily if you wet the walls of the hole with water. 
Do not force the glass tube into the hole roughly, but give it 
a twisting motion. 

Put into the wide-mouth bottle a layer of water so deep that 
the lower end of the funnel stem will reach just below the sur- 

1 




FIG. 1. 




2 LABORATORY EXERCISES 

face of the water. Close the second hole in the rubber stopper 
by means of a glass plug or a round pencil. See that the 

rubber stopper is pressed tightly into the mouth of 

the bottle; then pour water into the funnel, keeping 

the funnel full. 

Does any water run into the bottle? Does it 

continue to run in? Tell why. Now open the 

second hole of the stopper, and tell the result. 

Explain it. 

How do these experiments show that air takes 

up room? 

d. Examine a biscuit cutter. If you were making 
FIG. 2. one out of a tin box cover, why would it be a good 

plan to make a hole in the top? 

Where is the faucet inserted into a vinegar or molasses 
barrel? Why is a small hole (vent) drilled into the top of the 
barrel? Is there any similar opening in the sewing-machine 
oil-can or the oil-can used by carpenters? How is oil obtained 
from such a can? Why? 

e. Simpler Form. You can carry out the 
experiment of c with a small-mouth bottle, such 
as a vinegar or ketchup bottle, and a kitchen 
funnel (Fig. 3). Make the opening of the funnel 
stem smaller by closing it partly by means of a 
wooden plug, such as a pencil. Put the funnel 
stem loosely into the mouth of the bottle, and 
pour water into the funnel. How does the water 
run into the bottle, in a stream or by spurts? 
Now wind around the funnel stem a strip (about 
1 cm. wide) of wet muslin, until the funnel 
stem can be fitted tightly into the mouth of 
the bottle. Then pour water into the funnel, 
and tell how the water enters the bottle. FIG. 3. 




HOW TO MEASURE LENGTH AND AREA 3 

EXERCISE 2 

HOW TO MEASURE LENGTH AND AREA 

Apparatus. Meter stick, table. 

a. Examine a meter stick. How many decimeters long is it? 
How many centimeters? How many millimeters? How 
many inches? 

b. With a ruler graduated in English units draw in your note- 
book a horizontal line exactly 5 inches long. To make the 
length accurate put the edge of the ruler against the paper, and 
mark the ends of the line by means of a sharp-pointed pencil. 
Now measure the line with the metric rule, and state its length 
in centimeters and tenths of a centimeter. 

c. Measure, in centimeters, the dimensions of the top of your 
laboratory table or of a kitchen table. Measure also the thick- 
ness of the table top. Calculate how large a piece of oilcloth, 
in square centimeters, you would need to cover the table top 
and its edges, including the necessary slight lapping at each of 
the four corners. From the table of equivalents given in the 
appendix of the text calculate the number of square inches of 
oilcloth needed. Change this area to square feet. To square 
yards. Give all your work. 

d. Record your results thus : 

Length of table top, in cm. 
Width of table top, in cm. 
Thickness of table top, in cm. 
Length of oilcloth needed. 
Width of oilcloth needed. 
Area of oilcloth, in sq. cm. 
Area of oilcloth, in sq. in. 
Area of oilcloth, in sq. ft. 
Area of oilcloth, in sq. yds. 



LABORATORY EXERCISES 



EXERCISE 3 
THE MEASURING OF VOLUME AND CAPACITY 

Apparatus. Two cubical blocks, metric rule, a marble about 1 in. 
in diameter, graduated cylinder, half-pint measuring cup with vertical 
sides. 

a. The Volume of a Marble. Place two cubical blocks 
tightly against the edge of a metric rule (Fig. 4), and between 
the blocks place a spherical marble. By measuring the dis- 
tance between the two blocks get the diameter of the marble 
in centimeters and tenths. Mathematics teaches us that the 
volume of a sphere is very nearly ^X^X the cube of the 



Fia. 4. 

diameter. Suppose that the marble is 2 cm. in diameter; the 
volume of the marble would be eX-y-XS, or 4.19+ cu. cm. 
In the same way calculate the volume of the marble given 
you, and record it, together with all your work. 

Volume by Displacement. We can also get the volume of 
the marble by finding out how much water the marble can push 
out of the way, or displace, (Fig. 5 of text) . Half fill a graduated 
cylinder with water, and read the water level accurately. To 
do this, have your eye on a level with the water, and read the 
mark at the under edge of the curved surface (meniscus). Put 
down the reading. Now put the marble into the water, and 
read the new level. Subtract the first from the second reading. 
What is the volume of the marble by this method? Compare 
the two results. 

Record your results systematically, as in Exercise 2. 



HOW TO WEIGH 5 

b. The Capacity of a Measuring Cup. Examine a measur- 
ing cup with vertical sides. We can calculate its capacity, or 
how much it holds, in cubic centimeters, as follows: 

Measure carefully the inside, vertical height, from the bot- 
tom of the cup to the lower edge of a ruler, or block, placed 
across the top. Have it accurate to 0.1 of a cm. Measure also 
the greatest inside distance across the top (the diameter). The 
capacity of the cup is equal to the height multiplied by -^XjX 
the square of the diameter. Suppose that a cup has a diameter 
of 3 cm., and a height of 4 cm. The capacity of the cup 
would be 4X^XiX9, or 28.28+ cu. cm. 

How many cubic centimeters does your cup hold? Fill the 
cup with water, then pour the water carefully into a graduated 
cylinder. How does your calculated result compare with that 
shown by the cylinder? 

Use the table of equivalents in the Appendix of the text to 
find the capacity of your cup in cubic inches. A gallon is 
equivalent to 231 cu. in. How many of your cupfuls are there 
in a gallon? In a quart? In a pint? Does your measuring 
cup seem to be fairly accurate, as judged by the number of 
cupfuls in a pint? 

EXERCISE 4 
HOW TO WEIGH 

Apparatus and Materials. Balances, weights, shot, graduated 
cylinder, measuring cup or beaker, water. 

a. Balances. We weigh objects by means of balances or 
scales (see Figs. 9, 10, and 11 of the text). Fig. 5 (this manual) 
represents some home-made scales; they can be hung from an 
overhead support, such as the edge of a shelf or the ring of a 
ring stand. The beam is of galvanized iron or sheet copper; 
the pans may be the covers of small baking-powder boxes; the 



6 LABORATORY EXERCISES 

3 rings of the beam are made of metal (brass or plated iron), so 
that they shall have little friction against the beam. A con- 
venient length for the beam is 18 cm. (7+ in.). 

b. Rules for Weighing: 

1. Put the object to be weighed on the left-hand pan, the weights 
on the right. Handle the weights with forceps if possible. 

2. Do not drop the weights on the pan, but set them down care- 
fully. 

3. Do not leave the balance beam swinging when the balance is not 
in use. 

4. Do not weigh an object directly upon the pan. Put a dish or a 

piece of paper on the left-hand pan, 
counterpoise, or balance, it exactly with 





weights or shot placed in the right-hand 
pan, and then put the object in the 
balanced pan or paper. 

5. Learn just what weights ought to 
be in your case, and see that all are 
there before you begin weighing. When 
you have balanced the object you are 
weighing, count up what weights are 

gone from your case; these should be the ones on the balance pan. 

Finally, take off all the weights used, set them in a row on a clean 

piece of paper, and count them up to see if you added them correctly 

before. 

6. Record all your weights while you are at the balance. Do not 
try to carry the number "in your head" until you return to your desk. 
Put down all your weights in grams and decimals (tenths or hun- 
dredths). 

7. Label all your figures at once, so that you will know to what object 
or material they belong. 

8. When you are through weighing, return all weights to their proper 
places in the case, and leave the case and the balance in good condition. 

c. Weight of a Given Volume of Water. In a graduated 



PLUMB LINE AND PENDULUM 7 

cylinder measure out carefully 25 cu. cm. of water. Get the 
weight of an empty dish, such as a measuring cup; then pour all 
of the water into it. Weigh the cup and the water, and cal- 
culate the weight of the 25 cu. cm. of water. How much 
would 1 cu. cm. of water weigh, according to your result? How 
much would a liter of water weigh? What is the .accurate 
weight of 1 cu. cm. of water at 4 C.? Of a liter? 

From the result of Exercise 3 tell how many cubic centimeters 
there are in a cupful. How many grams of water are there, 
consequently, in a cupful? From the Appendix (text) find out 
how many grams there are in an ounce. How many oimces 
of water, then, in a cupful? How many ounces in a pint? 

Is it true that 

"A pint's a pound, 
The world around"? 

What fraction of a pint does a "4-oz." bottle hold? 
Record your results thus: 

Wt. of cup + 25 cu. cm. of water = g. 

Wt. of cup alone .= g. 

Wt. of 25 cu. cm. of water = g. 

Wt. of 1 cu. cm. of water = g. 

Accurate wt. of 1 cu. cm. water at 4 C. = g. 

Accurate wt. of 1 liter water at 4 C = g. 

Wt. of water in a etipful = g. 

Wt. of water in a cupful = oz. 

Wt. of water in a pint = oz. 

EXERCISE 5 
PLUMB LINE AND PENDULUM 

Apparatus. A small, dense object, such as a metal ball, a bullet, a 
stone, or a key; also some thread. 



8 LABORATORY EXERCISES 

a. Suspend the ball or other object by means of a light 
thread or string, so that it will swing freely. The thread may 
be tied to a gas fixture or a similar support. The ball or weight 
so suspended is called the "bob." What position do the bob 
and string take when left at rest? Why are they together called 
a plumb line? For what is a plumb line used? When does it 
become a pendulum? What is the meaning of pendulum? 

b. Draw your plumb line aside, and let it go. What happens? 
When a body has been set in motion, the amount of the motion 
is called the momentum of the body. Momentum depends on 
both, the mass (weight) of the body and its velocity. A body 
weighing 10 grams and having a velocity of 10 meters a second 
has the same momentum as a body weighing 1 gram and having 
a velocity of 100 meters a second. What makes the pendulum 
swing? Why does it not stop when the bob is at its lowest 
point? Will the pendulum ever stop swinging? What has the 
air to do with stopping it? If the pendulum string or thread 
rubs (has friction) against its support, what will the effect of 
this rubbing be? What device keeps a clock pendulum in 
motion? 

Why is a hammock a pendulum? When you are swinging 
in a hammock, what do you do that corresponds to the slight 
push of the clock spring? When, in a swing, you "let the old 
cat die," what do you depend on to keep you swinging? What 
finally stops the swing? 

c. Make the thread or string of a pendulum about 120 cm. 
(4 ft.) long, and tie it so that the distance from the point of 
suspension to the center of the bob is very close to 1 meter 
(39.37 in.). Set the pendulum swinging, and count the number 
of swings (vibrations) that the pendulum makes in 1 minute. 
Do this 3 times, add the results together, and divide by 3. 
What is the average number of swings per minute? Adjust 
the length of the thread so that the pendulum shall swing once 



INERTIA AND CENTRIFUGAL FORCE 9 

a second. About how long, then, is a pendulum that swings 
once a second? 

Make the pendulum 25 cm. long (how many inches is this?), 
and count the number of vibrations in a second. Get the aver- 
age of 3 trials, as before. 

If you can find a high enough point of suspension (a stick 
placed horizontally out of an upper window will do), make a 
pendulum 4 meters long, and find out how many vibrations it 
makes in a minute. What is the time of one vibration? If we 
have two pendulums, and one is 4 times as long as the other, 
compare the amounts of time which they will take to swing. 



EXERCISE 6 
INERTIA AND CENTRIFUGAL FORCE 

Apparatus and Materials. Wooden blocks, calling card, coin, flat- 
iron, strong cord, thread, ball with a rubber cord, small pail with a 
handle, water. 

a. Try the experiment suggested in the text, 29, exercise 4. 

6. Hold out your left hand, palm upward. Near the tip of 
your first or your middle finger place a calling card, and on the 
card, just over your finger, put a coin, such as a nickel. Prac- 
tice snapping the edge of the card with the thumb and a finger 
of your right hand, until you can drive the card away horizon- 
tally, leaving the coin on your finger. Explain why this is 
possible. 

c. Suspend a flatiron by means of a stout cord, so that it 
escapes the floor by a few centimeters (an inch or two). Have 
the cord as long as is convenient. Tie a piece of thread (not 
too strong) to the flatiron, and by gentle pulling, properly 
timed, set the flatiron pendulum to swinging. When the 



10 LABORATORY EXERCISES 

iron is swinging freely, try to stop it by a sudden pull on the 
thread. What happens? Why? 

Now stop the flatiron, attach the thread once more, and try 
to set the iron to swinging by giving a sudden pull on the 
thread. What happens? Why? 

d. Tie to a small ball a rubber band or cord, and (out of 
doors, or where you cannot break a window) whirl the ball 
slowly about your hand. What is the effect upon the rubber 
as you whirl the ball mo"re and more rapidly? What does this 
indicate as to the intensity of the force exerted on the ball as 
the speed of the ball increases? 

e. Into a small pail put about a cupful of water, and whirl 
the pail around rapidly in as large a circle as you can. Does 
the water fall out when the pail is upside down? How is it possi- 
ble for a car to "loop the loop"? 

EXERCISE 7 
ADHESION OF LIQUIDS TO SOLIDS; LIQUID SURFACES 

Apparatus and Materials. Mercury, glass tube or rod, water, glass 
or beaker, vaseline (or grease or machine oil), nail, silver spoon, pencil, 
sheet of glass, iron stove lid or sheet of iron, graduated cylinder, needle, 
bowl. 

a. Into a dish containing mercury dip a clean glass tube or 
rod; then remove it. Does the mercury wet the glass? What 
form has the surface of the mercury where the tube (or rod) 
enters it? Make a drawing of it. Now dip the glass tube into 
water. What is the form of the surface about the tube. Draw 
this surface also. 

What is the shape of a water surface near the sides of a glass 
dish? 

b. Thoroughly cover the inside of a water glass or beaker 
with a thin layer of vaseline or lard; then partly fill the glass 



ADHESION OF LIQUIDS TO SOLIDS; LIQUID SURFACES 11 

with water. What is the shape of the edge of the water sur- 
face? Dip into the water a glass tube or rod that is covered 
with grease or vaseline. What is the shape of the surface 
around the tube (or rod)? 

If a liquid wets a solid, will the liquid surface be lifted up, or 
pushed down, next to the solid? If the liquid does not wet the 
solid, what will the result be? What is the effect on the liquid 
surface when you dip a nail into water? A silver spoon? A 
pencil? 

c. Put a drop of water upon a freshly washed, but dry, 
piece of glass. What shape does the drop take? Draw a 
sketch showing this. Put a drop of water upon a greased paper. 
Its shape? On a kneading board dusted with flour. The 
result? 

d. Put a drop of water on a stove top that is not red hot. 
What is the shape of the drop? Then put a drop of water upon 
a red-hot sheet of iron, such as a stove lid. What is the shape 
now? If your family uses a gas range, put a thin sheet of iron 
(a piece of "tinned" iron or a flat "tin" cover will do) over the 
gas flame until it is red hot; then add the water drop. 

e. Let water drop into a graduated cylinder, ami count the 
number of drops in 10 cu. cm. You can get water to form drops 
on a faucet, or you can make a tiny hole in the bottom of an 
empty tin can, so that the water will leak out drop by drop. 
Make at least three trials, and get the average. Calculate how 
many drops of water there are, under ordinary conditions, in 
1 cu. cm. Put down all results in systematic form, as in 
Exercise 2. Make a sketch showing the stages in the formation 
of a water drop. 

/. Wipe a needle clean, and then oil it very slightly with 
vaseline or machine oil. Hold the needle horizontal on a fork; 
then lower the fork carefully into a bowl or soup plate of water. 
The needle should float. Examine the water surface, and tell 



12 LABORATORY EXERCISES 

why. If you do not succeed the first time, dry the needle and 
the fork carefully, and try again. 

EXERCISE 8 
CAPILLARY ACTION 

Apparatus and Materials. Bunsen burner, glass tube about 15 cm. 
long, colored water or ink, two glass vessels (beakers or water glasses), 
strip of cotton cloth (or of blotting paper), concentrated salt brine. 

a. Heat the middle of a piece of glass tubing in a Bunsen 
flame until it is soft enough to be drawn out. You will need 
to hold both ends of the tube in your hands, and to turn the tube 
rapidly at first so that it can be heated evenly. Do not draw 
the tube out until its walls have almost melted together. Then 
remove the tube from the flame, and draw it out at once. In 
this way you can get a long tube of a .very small diameter 
(a capillary tube). 

6. When the tube is cool, break it carefully at its narrowest 
part, and then dip the small end into a dish of colored water, 
or into ink. Note how the liquid ascends into the tube. What 
is the shape of the liquid surface in the capillary tube? If 
different parts of the tube are of different diameters, break 
the tube so as to get two capillary tubes, one of a considerably 
larger diameter than the other. Dip both into the liquid. In 
which one does the water ascend to the greater height? 

c. Try the experiment shown in Fig. 25, 32, of the text. 
Use a wet cotton cloth, a wet strip of blotting paper, or a wet 
string. 

d. Into a clean, dry water-glass pour carefully about 10 cu. 
cm. of a concentrated salt brine. Pour the salt solution down 
the side of a glass tube or rod (c/. 84, Fig. 68, of text) so that 
the solution does not wet the sides of the glass above the liquid 
level. Mark the level of the liquid by means of a piece of paper 



DENSITY 13 

pasted on the outside of the glass. Now set the glass aside in a 
warm place, and watch it from day to day. What happens? 
Remembering that there is a narrow space between the crust of 
salt and the side of the glass, tell why the salt crawls up the 
glass. What is the shape of the salt crystals in the bottom of 
the glass? 

EXERCISE 9 
DENSITY 

Apparatus and Materials. Block of wood, metric rule, balances, 
graduated cylinder, kerosene, shot. 

a. Density of Wood. Measure carefully, to a millimeter, 
the dimensions of a block of wood. A toy block will do. The 
block must have rectangular or square faces. If, in measuring 
any one of the dimensions of the block, say, the length, you 
find that the distances along the four edges of the block are 
not equal, take the mean length. That is, add the 4 lengths 
together, and divide the sum by 4. In the same way get 
the other two dimensions of the block, and then calculate 
the volume of the block, in cubic centimeters. Now weigh the 
block carefully, in grams and tenths; then divide the weight, 
in grams, by the volume, in cubic centimeters. 

How many grams are there for each cubic centimeter? This 
is the density, in grams per cu. cm. Of what kind of wood does 
the block consist? Compare the density you have found with 
that given in the Appendix of the text. 

6. Density of Liquids. Pour a little kerosene into a test 
tube, and add some water to the tube. Do the liquids become 
mixed? Which has the smaller density? 

Whittle a stick of wood (pine or white wood) to about the 
thickness of a pencil and the length of a test tube. Put it into 
a test tube that is nearly full of water. Note how far it sinks 



14 LABORATORY EXERCISES 

into the water, and mark this point on the stick. Then wipe 
the stick dry and put it into a test tube of kerosene. Does it 
sink farther than in water, or not so far? Why? 

From Exercise 4, b, tell the density of water, under ordinary 
conditions, in grams per cubic centimeter. Using the method 
of Exercise 4, find the weight of 25 cu. cm. of kerosene. Calcu- 
late how many grams 1 cu. cm. weighs (the density) . Compare 
your result with that in the Appendix. 

c. Density of Shot. Take shot enough to fill about ^ of 
your graduated cylinder, and get the weight of the shot. Have 
the cylinder about half full of water, and get the volume 
accurately. Be sure to read to the bottom of the curved sur- 
face (meniscus). Then put the shot into the cylinder, and 
read the new height of the water. Be sure that no air bubbles 
are caught between the grains of shot. What is the volume 
of the shot? What was its weight? Calculate the weight of 
1 cu. cm. Of what is shot made? What is its density? 

Record all the results of this exercise systematically, as in 
Exercises 2 and 4. 

EXERCISE 10 
WEIGHT OF A STONE IN AIR AND IN WATER 

Apparatus and Materials. Balances (or scales), stone, thread, 
beaker (or glass), water. 

a. In order to carry out this exercise we first weigh a stone 
in air, as usual; we then suspend it from a balance and get the 
weight it has when in water. The method of suspending the 
stone depends on the kind of a balance we use. Fig. 6 shows 
how to do it with a chemical balance; Fig. 7 is for a Trip scale; 
Fig. 28, in 34 of the text, shows a third way. A spring bal- 
ance (Fig. 11 of text) may also be used. 

Get the weight, in grams and tenths, of the stone and a 



CENTER OF MASS 



15 



piece of thread. Then tie the thread to the balance so that 
the stone is entirely immersed in water, but does not touch 
the sides or bottom of the vessel holding the water. Find the 
weight of the stone in this position; is it the same as before? 
What is the exact amount of difference? 





FIG. 6. 



FIG. 7. 



6. Remember that water is pushed out of the way by the 
stone, and that this water exerts force in pushing up, or buoy- 
ing up, the stone. How many grams of water, then, has the 
stone pushed out of the way? If this water were at 4 C., 
what would its volume be? What, then, is the volume of the 
stone? Record your results systematically. 



EXERCISE 11 
CENTER OF MASS 

Apparatus and Materials. Cork, cork-borer or small file (rat-tail 
or triangular), shot, toy called a " tumbler," Mason fruit jar, pail of 
water. ..,, 

a. In a large cork bore a hole lengthwise, at one side of the 
center (Fig. 8) . If you have no cork-borer, you can use a small 
file or the small blade of a penknife. Fill the hole with shot 
packed in tightly, and hold the shot in place with wads of paper 




16 LABORATORY EXERCISES 

or cotton. What happens when you lay the cork on its side on 
the table? Try various positions. Account for what happens. 
Examine the toy called a " tumbler"; why does it always 
come to an upright position? 

b. Seal tightly an empty Mason fruit 
jar, and lay it on its side in a pail of 
water. Does the bottle rest equally well, 
however you place it, or does it come to 
rest in some preferred position? Tell 
why. 

c. Take the cover off from a Mason fruit 
jar and try to stand the bottle upright 
on the water. Explain what happens. 

Now put water into the jar until the jar floats right side up. 
Give the explanation. 

Why do you hold out your hands when walking a rail? Why 
does a tight-rope performer carry a long pole? Why does a 
ship carry ballast? 

EXERCISE 12 
PRESSURE OF THE ATMOSPHERE 

Apparatus and Materials. Glass tube, medicine dropper, water, 
mercury, glass siphon (either prepared or to be made by the student; 
if to be made, a glass tube about 30 cm. long may be used). 

a. Put one end of a glass tube into a glass of water, and by 
suction remove the air from the tube. What happens? Why? 

6. Put the open end of a medicine dropper under water, 
and pinch the rubber bulb. What happens? Let go of the 
bulb, and state the result. Why does the bulb expand when 
released? What effect has this upon the pressure of the air in 
the bulb? What causes the water to rise? 

c. If there is mercury in the laboratory, put the open end of 



PRESSURE OF WATER AND OF AIR 



17 




FIG. 9. 



the medicine dropper under the mercury, pinch the bulb so as 
to expel the air as completely as possible, and then release it. 
Does the bulb expand completely? Why? 

d. Siphon. Put the shorter arm of the bent tube (Fig. 9; 
make this, if necessary, as in 4 of the Introduction) into a 
vessel of clean water, and suck the 
air out of the longer arm. What 
happens? Continue removing the 
air until the longer arm is full of 
water; then remove your mouth, and 
note what .happens. Place an empty 
vessel under the longer arm. Have 
the top of the second vessel slightly . 
higher than the bottom of the first 
one. How long does the water run? The bent tube with the 
water flowing through it is a siphon. How far above the 
water level of the first vessel may the bend of the siphon be? 
What pushes the water up to the bend of the siphon? What 
pulls it down in the longer arm? 

Pour the water back into the higher vessel, and fill the siphon 
with water by immersing it in a pail of water or by holding it 
under a faucet of running water. Close the opening of the 
longer arm with your finger, and put the shorter arm into the 
higher vessel; then remove your finger, and note the result. 

For what purposes may a siphon be used? 

EXERCISE 13 
PRESSURE OF WATER AND OF AIR 

Apparatus and Materials. Deep glass vessel, small glass vial, wire, 
and stick (or glass tube); wide-mouth bottle, two-hole stopper (one 
hole plugged), bent glass tube. 

a. Fill with water the deepest glass dish you can find. A 



i 




18 LABORATORY EXERCISES 

two-quart fruit jar or a tall vase will do. Fasten a small vial 
or test tube (mouth downward) to a wire or stick, and push it 
slowly to the bottom of the water. What happens to the vol- 
ume of the air in the vial or test tube? Why? What relation 
does there seem to be between the depth of the water and the 
pressure of the water? 

6. The Diver. Arrange the bottle and other apparatus 
shown in Fig. 10. The vial is partly full of air and 
partly of water; it should just float. Put the stop- 
per tightly into the bottle, and blow air through 
the tube. What is the result? Then let. the extra 
air escape. What happens to the vial? Now, in- 
stead of blowing air into the bottle, remove air, by 
suction, from the bottle, and tell the result. 

What is the explanation of the behavior of the 
vial? Draw three sketches showing the position of 
the vial, and of the air and water in it, at ordinary 
pressure, at increased pressure, and at reduced 
pressure. Compare the behavior of the diver with that of a 
submarine boat. 

EXERCISE 14 
COLLECTING A GAS OVER WATER 

Apparatus and Materials. Wide-mouth bottle (small), pan of water, 
glass tube, wooden splinter, test tube, illuminating gas. 

a. Fill a wide-mouth bottle completely with water, and 
cover the mouth of the bottle with a piece of wet writing paper. 
With your hand hold the paper in place, so that no air bubbles 
remain in the bottle. Then invert the bottle over a pan of 
water, but do not, at first, put it into the water. If you are 
careful, you can remove your hand from the paper, and the 
water will not fall out. What supports the water? 



SUBSTANCES PRODUCED IN BREATHING AND BURNING 19 

Now put the mouth of the bottle under water, and remove 
the paper. Why does not the water fall out? How tall might 
the bottle be, and yet remain full of water when inverted in 
water? 

Through a glass tube blow your breath (see Fig. 37, 45, of 
the text), and catch the gas bubbles by the displacement of the 
water in the bottle. When the bottle is full, slip the wet piece 
of paper under it, hold the wet paper tightly against the 
bottle's mouth, and set the bottle upright on the table. Put 
into the bottle of gas a lighted splinter or match. Does the 
gas take fire? Does the splinter (or match) continue to burn 
in the gas? 

6. In a similar way fill a test tube with water, and then fill 
the tube, by water displacement, with illuminating gas. Get 
the gas from a tube connected with the gas outlet. Carefully 
light the test tube of gas. 

EXERCISE 15 
SUBSTANCES PRODUCED IN BREATHING AND BURNING 

Apparatus and Materials.^- An acid (vinegar or hydrochloric acid), 
test tubes, limewater, glass tube, wide-mouth bottle, cardboard cover, 
splinter, candle, wire for a holder, marble or soda. 

a. Prepare some carbon dioxide in a test tube by adding an 
acid, such as vinegar or dilute hydrochloric acid, to some marble 
or soda that is in the test tube. Hold the mouth of the test 
tube over the mouth of another test tube as if you were going to 
pour a liquid from the one into the other, but do not actually 
pour any of the liquid. The invisible gas carbon dioxide is thus 
poured over. 

Add to the test tube that now contains carbon dioxide about 
5 cu. cm. of limewater, close the test tube with the thumb, and 
shake the tube, so that the gas is mixed with the liquid. What 



20 LABORATORY EXERCISES 

is the result? The fact that the limewater becomes milky 
serves as a test for carbon dioxide. 

6. Through a glass tube blow your breath for some time into 
about 5 cu. cm. of limewater. Have the limewater in a test tube. 
What happens? What gas must be present in exhaled air? 

c. Prepare a. cardboard cover for a wide-mouth bottle, and 
make in the cardboard a hole just large enough to hold firmly 
a pine splinter about half as thick as a pencil. The splinter 
should be long enough to reach almost to the bottom of the 
bottle. Light the splinter, and put it into the bottle, using the 
cardboard both to cover the bottle and to hold the splinter. 

Let the burning go on as long as it will. Why does the 
splinter not burn until it is all consumed? Is there any sign 
that water is formed in the burning? Now remove the splinter, 
put into the bottle about 5 cu. cm. of limewater, close the 
bottle, and shake it. What is the result? What gas must be 
formed when wood is burned? 

d. Burn a small candle (use a wire as a holder) in a bottle of 
air, and make the same tests as in c. Give all the results, and 
explain them. 

EXERCISE 16 
HEATING OF TIN IN AIR 

Apparatus and Materials. Small iron dish (cake tin or cover of 
baking-powder box), stout wire or a small file, tin, ring stand, balances. 

a. Weigh, all together, a small iron dish containing about 
10 g. of tin, and a piece of stout iron wire that is to be used as a 
stirring rod. Instead of the wire a small file may be used. 
Support the dish on a ring stand (Fig. 11), and heat it strongly, 
stirring the melted tin with the wire or the reverse end of the 
file. What happens to the tin? If the wire or file becomes hot, 
put one end into a cork, or a spool, and use this as a handle. 



PREPARING OXYGEN 



21 




FIG. 11. 
A Home-Made Ring Stand. 



Continue to push the scum to one side, so that the bright 
surface of the tin is kept in contact with the air. If the scum 
formed contains the tin and some- 
thing taken from the air, do you 
think the dish, its contents, and the 
wire, taken together, will weigh more, 
or less, than they did before the 
heating? Keep up the heating for, 
say, 15 minutes, then let the ap- 
paratus cool, and weigh it again. 
What is the result? How much 
matter was taken from the air? 

b. If you have no balances, carry out the heating without the 
weighing. You can do the experiment at home, if necessary, 
using a box cover for the iron dish, and the stove for the source 
of heat. 

EXERCISE 17 
PREPARING OXYGEN 

Apparatus and Materials. Wide-mouth bottle, stopper (two-hole), 
dropping funnel (or ordinary form), glass rod, delivery tube, pan of 
water; potassium permanganate or manganese dioxide, hydrogen 
peroxide, splinter, candle, limewater. 

a. Prepare oxygen, if possible, in the ap- 
paratus shown in Fig. 44, 51, of the text. If 
you have no dropping funnel, you can use an 
ordinary funnel with a glass rod to control the 
size of the opening into the stem (Fig. 12). A 
short piece of rubber tubing placed over the end 
of the rod will make a tighter joint than the 
glass alone. 

b. Simpler Form. You can make the oxygen 
FIG. 12. more easily if you put the potassium permangan- 




22 LABORATORY EXERCISES 

ate and hydrogen peroxide into a small, wide-mouth bottle. 
Use only a cardboard or glass cover. (See Fig. 18, Exercise 36.) 
The oxygen simply expels the air. About 3 cu. cm. of potassium 
permanganate is enough; the hydrogen peroxide can be added 
a few cu. cm. at a time. In place of the potassium permangan- 
ate you can use about 5 cu. cm. of manganese dioxide. Add 
the hydrogen peroxide as already directed. 

c. In whatever way you prepare oxygen, put into a bottle of 
it a small burning candle supported by a wire. Describe the 
burning of the candle. Then remove the candle, and pour the 
gas in the bottle into a test tube containing a little limewater. 
Be sure you do not pour out any of the liquid (see Exercise 15). 
Shake the limewater and the gas. What is the result? Com- 
pare the product formed when the candle burns in oxygen with 
that formed when it burns in air. What conclusion can you 
draw from this fact? 

d. Put into the bottle in which oxygen is being formed a pine 
splinter with a glowing (not a flaming) tip. What happens? 
How could you tell a bottle of oxygen from one of air? 

Let the splinter burn for some time in the bottle of oxygen; 
then test the gas in the bottle to see if it contains carbon dioxide. 
Give your result. 

EXERCISE 18 
AIR DISSOLVES IN WATER 

Apparatus and Materials. A water glass, fruit jar, pan of water, 
burner or stove, pail of water, test tube, splinter. 

a. Fill a glass or bottle with fresh, cold water, and let it 
stand in a warm place, near a stove or radiator, for an hour 
or two. What collects on the sides of the dish? Where did 
it come from? 

b. Fill a glass fruit jar entirely with fresh, cold faucet or well 
water, cover the mouth of the jar with a wet paper (see Exer- 



NITROGEN; THE COMPOSITION OF AIR 



23 



else 14), and invert the jar in a pan containing water to the 
depth of an inch or two. Then raise the temperature of the 
water in the pan to boiling, and continue the boiling for 15 or 
20 minutes. What collects in the upper part of the inverted 
glass jar? 

Let the jar and its contents become moderately cool; then 
cover the mouth of the jar with moist paper, and remove the 
j ar to a pail of water. Now transfer the gas, under water, from 
the jar to a test tube of water (see Fig. 78, 102, of the text). 
Close the test tube with the thumb, invert it, and put into the 
gas a burning splinter. Does the gas act like air, or not? 



EXERCISE 19 
NITROGEN; THE COMPOSITION OF AIR 

Apparatus and Materials. Test tube, beaker, 10% solution of 
potassium hydroxide (or sodium hydroxide), "mossy" (granulated) 
tin (or iron filings), pail of water, graduated cylinder. 

a. We can find out what the nitrogen of the air is like by 
removing the oxygen. Certain metals moistened with a solu- 
tion of potassium hydroxide or sodium hydroxide 
readily unite with the oxygen. We make use of 
this fact in the following experiment (Fig. 13) : 

Into a test tube put a piece of " mossy" tin of 
such a size that it sticks slightly when pushed 
into the tube. Pour into the test tube about 
10 cu. cm. of 10% potassium hydroxide solu- 
tion, wetting the tin thoroughly; then pour the 
solution out into a small beaker. Now set the 
tube, mouth down and vertical, into the beaker, 
and let it stand over night. 

6. What change do you notice? By holding 
your ruler upright beside the test tube estimate FlG . 13. 



24 LABORATORY EXERCISES 

what fractional part of the air has disappeared? Is it J^, or 
H, or what? What gas was taken out of the air that was in 
the test tube? What gas remains? 

c. Put the beaker and test tube into a pail of water, so that 
you can remove the test tube from the beaker without getting 
the mouth of the test tube above the liquid. Then close the 
mouth of the test tube with your thumb, remove the tube 
from the water, and turn the tube right side up. Put a burning 
match into the gas. Does the gas burn? Does the match con- 
tinue to burn? How can you distinguish between nitrogen, air, 
oxygen, and illuminating gas? 

d. If you wish to get a more exact result for the amount of 
oxygen in air, measure in a graduated cylinder the amount of 
water that entered the test tube. Then, leaving the tin in the 
tube, fill the tube entirely with water, and get the volume of 
the water. This equals the volume of the air originally in the 
tube. From the results find the per cent of oxygen in air; that 
is, the number of parts of oxygen in every 100 parts of air. 

e. Iron filings and 10% sodium hydroxide solution may be 
used instead of tin and potassium hydroxide, but the reaction is 
somewhat more slow. Wet the inside of the test tube with 
10 cu. cm. of 10% sodium hydroxide solution, and pour the 
solution into a beaker. Put into the tube about 1 cu. cm. of 
iron filings, spreading them out in the closed end of the tube. 
Then set the tube, mouth down, into the beaker, and let the 
apparatus stand for one or two days. 

EXERCISE 20 
EXPANSION AND CONTRACTION OF WATER 

Apparatus and Materials. Flask with one-hole stopper and long 
glass tube, gummed paper (or thread), ring stand, flame, pail of hot 
water, long-necked bottle. 




EXPANSION AND CONTRACTION OF AIR 25 

a. Have a flask fitted with a one-hole stopper and a glass tube 
as shown in Fig. 14. Fill the flask with water, and press the 
stopper tightly into it; the water will rise part way up the 
tube. Mark the level of the water in the tube by means of a 
strip of gummed paper or a thread; then dry the flask 
and put it on wire gauze placed on a -ring stand. 

Heat the flask carefully with a small flame. Note 
all the changes that occur in the water level, and 
explain them. Do not heat the water to boiling, 
or until it actually overflows. 

Let the flask cool, and then put it into a dish of 
cold water, or hold it under a cold-water faucet. 
What happens? 

6. Instead of heating the flask over a flame you 
can plunge it into a pail of hot water. Note the 
first effect upon the level of the water, and the effect as heat- 
ing is continued. Explain each effect. 

c. Simpler Form. Instead of a flask you can use a bottle 
with a long neck, such as a household-ammonia bottle, or a 
vinegar bottle. No stopper or tube will be needed. Mark 
the level of the water carefully (it should be a few centimeters 
below the mouth of the bottle), put the bottle in a pail of water, 
and heat the water in the pail; or you can set the bottle in a 
warm place, as, for example, near a radiator or a stove, for an 
hour or two. Note the change (or changes) in the level of the 
water, and explain. Then let the bottle cool, and note the 
results. If possible, set it in a cold place, but do not let it freeze. 

EXERCISE 21 
EXPANSION AND CONTRACTION OF AIR 

Apparatus and Materials. Flask or small-mouth bottle, pan of 
water, drinking glass, saucer. 



26 LABORATORY EXERCISES 

a. Put a cold flask or small-mouth bottle (Fig. 52, 61, of 
the text) mouth down in a pan of water, and grasp the flask in 
both hands, so as to warm it. What happens? Why? 

Warm the flask more, either by heating it carefully, or by 
pouring warm water over it. Results? Then let the flask cool, 
and note what happens. 

b. Set an empty drinking glass, mouth down, in a saucer 
or pan of hot water, as is often done when washed dishes are 
drained. Explain all that happens, both at first and afterward, 
when the glass and the water cool to the ordinary temperature. 

c. A cup, upside down, is usually placed in the center of a 
meat pie. Find out why. 

EXERCISE 22 
MELTING POINT AND FREEZING POINT; A FREEZING MIXTURE 

Apparatus and Materials. Beaker or measuring cup, thermometer, 
crushed ice, salt, test tube. 

a. Into a beaker or a measuring cup put about 30 to 50 cu. 
cm. of finely crushed ice, and stir it with a thermometer. Keep 
the thermometer bulb entirely in the ice. Stir the ice until the 
mercury stops shrinking; that is, until the thermometer ceases 
to "fall." Then get the exact reading, and put it down. 

b. When you are sure that your reading of the melting point 
is final, add to the ice a tablespoonful of salt, and again stir the 
mixture with the thermometer. What is the lowest tempera- 
ture reached by the thermometer? For what are freezing 
mixtures used? 

c. Into the freezing mixture of b put a test tube containing 
about 5 cu. cm. of water. Rinse off any salt that may be on 
the thermometer, and with the . thermometer gently stir the 
water in the test tube. Keep the bulb of the thermometer 



CONDUCTION OF HEAT 27 

immersed, and note the temperature of the water as it begins to 
freeze. Compare it with the temperature at which ice melts. 

EXERCISE 23 
BOILING POINTS OF WATER AND ALCOHOL 

Apparatus and Materials. A thermometer reading above 100C., 
a flask or cup, a beaker, a test tube, a ring stand or other support, 
water, salt, and alcohol. 

a. Examine your thermometer, and be sure it reads above 
100 C. Place a flask that is half full of water over a flame, and 
heat the water to boiling (see Fig. 54, 62, of the text). Sus- 
pend, or hold, a thermometer in the flask. At first have the 
bulb in the boiling water; then hold it in the steam above the 
water. What is the boiling point of water, according to your 
thermometer? 

6. After you have found the boiling point of ordinary water, 
put into the water about % its volume of salt, and heat the 
water to boiling until as much as possible of the salt dissolves. 
What is the highest temperature reached now? 

c. In a beaker, or cup, of boiling water put a test tube con- 
taining about 5 cu. cm. of alcohol, and hold a thermometer in 
the test tube so that the bulb is just below the surface of the 
alcohol. At what temperature does the alcohol boil? 

EXERCISE 24 
CONDUCTION OF HEAT 

Apparatus and Materials. Iron and copper wires about 15 cm. 
long, glass tube or rod of same length, burner, test tube of water, test 
tube holder. 

a. Conduction by Iron, Copper, and Glass. In a flame hold 
a piece of iron wire and one of copper, each about 15 cm. long. 



28 



LABORATORY EXERCISES 



Hold the wires horizontal, and place them so that they are 
heated equally. Which wire first feels hot to the hand, and is 
therefore the better conductor of heat? 

Put one end of a piece of glass tubing (or a glass rod), about 
15 cm. long, into the flame, and heat it until the end is melted. 
Does the end in your hand become hot? Is glass a good con- 
ductor of heat? 

6. Conduction by Water. Hold or support at an angle of 
about 45 degrees a test tube that is M full of water (Fig. 15). 

If you hold the tube, use a test tube 
holder (a folded strip of paper will 
do). Place the holder about the 
lower part of the tube, and hold the 
tube in a small flame so that the 
flame may strike the upper part of 
the tube, but may be below the level 
of the water. If the flame strikes 
the tube above the water level, the 
glass may be cracked. Heat the 
water to boiling. Is the lower part 
Does water conduct heat as iron and 




FIG. 15. 



of the test tube hot? 
copper do? 



EXERCISE 25 
CONVECTION 

Apparatus and Materials. Test tube and holder, burner, large 
beaker or flask, wire gauze and ring stand, fine sawdust, candle. 

a. Convection in Water. Take a test tube 5 / 6 full of water, 
hold it by the upper part, and heat the lower part in a small 
flame. Is the heating now confined to the part near the burner? 
Tell why. Over a burner, and on a wire gauze, place a tall 
glass beaker or flask 5 / 6 full of water. Put into the water a 



IS HEAT USED UP WHEN A LIQUID IS CHANGED TO A GAS? 29 

small amount of fine sawdust or tiny shreds of paper. Warm 
the beaker slowly, and note any movements in the sawdust 
or paper. What is taking place in the water? What is the 
meaning of convection? How is the upper part of the liquid 
heated? Let the hot liquid cool, and note what movements 
take place. What is the direction taken by the cooler water? 
By the hotter water? 

6. Convection in Air. Open a door leading from a warm 
room into a cold room or hall. Hold a lighted candle at the 
top of the door opening; at the bottom. What is the direction 
of the air currents in each case? Tell why. 

Hold the lighted candle near the incoming air register of your 
house or schoolroom. Near the outgoing register. Over the 
hot- water or steam coils. Give the results. 

Why does so much dust collect on walls and ceilings over hot- 
air registers, and over steam and hot-water radiators? What 
does this show as to the direction taken by heated air? 



EXERCISE 26 
IS HEAT USED UP WHEN A LIQUID IS CHANGED TO A GAS? 

Apparatus and Materials. Ether or gasoline, water, thermometer, 
absorbent cotton, beaker or measuring cup, balances. 

NOTE. Ether and gasoline are very inflammable. Put out 
all flames when working with them. 

a. Pour a few drops of ether or gasoline into the palm of your 
hand, and let the liquid evaporate. What is the result? 
Explain it. 

Wet your hand with water having the temperature of the 
room, and wave it back and forth to make the water evaporate. 
Is there any change in temperature? 

6. If you have a thermometer, find out if the result is only 



30 LABORATORY EXERCISES 

imagination. Tie a bit of absorbent cotton about the bulb of 
the thermometer, put some gasoline on the thermometer, and 
wave the thermometer back and forth. Does the reading show 
any change? What is it? 

c. Get the weight of a beaker half full of water, and keep the 
water boiling for 10 minutes. Does the temperature change 
during the boiling? Test it with a thermometer. Has the 
amount of water changed? How much? 

If 536 calories of heat are needed to evaporate 1 gram of 
water at 100 C., how many calories were added to the water in 
the beaker? Where did the heat come from? How was it 
produced? 

EXERCISE 27 
KINDLING TEMPERATURE 

Apparatus. Burner, wire gauze. 

a. Hold or support a piece of wire gauze (it should be at least 
10 cm. square) about 5 cm. above the top of a Bunsen burner. 
Have the air holes at the base of the burner open. Now turn 
on the gas supply, and bring a burning match over the middle 
of the gauze. Does the gas take fire above, or below, the gauze? 
Prove that there is gas below the gauze. 

b. Let the gauze become cool, and then bring the middle of 
it down into a Bunsen flame. Does the flame go through the 
gauze? Why? Hold the gauze in the flame until it is red hot. 
Does the flame now go through the gauze? Tell why. 

EXERCISE 28 
MIXING MATERIALS OF DIFFERENT TEMPERATURES 

Apparatus and Materials. Measuring cup and woolen material to 
fasten around it, cardboard cover, thermometer, water, burner. 



CONTENTS OF NATURAL WATER 31 

a. Make a simple calorimeter out of a measuring cup around 
the sides and bottom of which you have sewed or pinned some 
woolen material, such as flannel. A piece of cardboard, with a 
hole for a thermometer, will do for a cover. If the cup is 
graduated in fourths, you can measure the water that is used 
by looking at the marks inside the cup. 

b. Put into the calorimeter 34 of a cupful of water at the 
ordinary temperature, and get the temperature accurately. 
Remove the cover for a moment, and put in }^ of a cupful of 
water at 50 C. Put on the cover, and stir the water with 
the thermometer. What is the temperature of the water now? 
How near does it come to the temperature midway between the 
ordinary temperature and 50 C.? 

c. Now pour out the water, put in 34 of a cupful at the 
ordinary temperature, and J/ a cupful at 50 C. Put on the 
cover, and stir the water thoroughly. What is the resulting 
temperature? How near is it to the temperature % of the way 
from the ordinary temperature to 50 C.? 

EXERCISE 29 
CONTENTS OF NATURAL WATER 

Apparatus and Materials. Beaker or measuring cup, flask (100 cu. 
cm.), cork stopper and glass delivery tube, test tube, watch glass or 
sheet of glass, tea kettle (?), water. 

a. Boil some hydrant water vigorously for 10 minutes, and 
then let it stand. What settles out? Where did it come 
from? How is a deposit formed on the inside of tea kettles, etc.? 

b. Distill water in the apparatus of Fig. 16. Half fill the 
flask with hydrant water, and support it in a ring stand. Have 
a piece of wire gauze between the flask and the flame. Use a 
cork stopper and a doubly bent delivery tube, and catch the 
distilled water in a test tube standing in a beaker of cold water. 



32 



LABORATORY EXERCISES 



What is a definition of distillation? What is the taste of dis- 
tilled water? 

If you have not the apparatus of Fig. 16, you can get some 
distilled water by inverting a small, clean pail over the nozzle 

of a tea kettle in which water is 
boiling. Catch the water that 
drops from the lower edge of the 
pail. 

c. Evaporate about 5 cu. cm. 
of distilled water on a watch glass 
placed over a cup or beaker of 
boiling water. If you have no 
watch glass, use a piece of clean 
sheet glass. Lay it perfectly hori- 
zontal, and put the water to be 
evaporated, a few drops at a time, 
upon the center of its upper sur- 
face. 

In the same way evaporate about 5 cu. cm. of hydrant water 
or well water. Which water leaves the greater residue? Why 
does distilled water leave any residue at all? 




FIG. 16. 



EXERCISE 30 
WATER TESTS 

Apparatus and Materials. Beakers or bottles (3), graduated cylin- 
der, cardboard or glass covers, dilute sulphuric acid, potassium per- 
manganate solution, distilled water, natural water, powdered calcium 
sulphate (gypsum or plaster of Paris), soap. 

a. Organic Matter in Water. Measure out 50 cu. cm. of 
distilled water, and put it into a clean glass vessel, such as a 
beaker. Add to it 2 cu. cm. of dilute sulphuric acid and one 
drop of potassium permanganate solution. 



FILTERING AND PRECIPITATING 33 

Then add the same amount of dilute sulphuric acid and of 
potassium permanganate to 50 cu. cm. of hydrant or well water, 
and to 50 cu. cm. of ditch, pond, or aquarium water. Cover 
the 3 vessels with cardboard or glass covers, and set them aside 
in a warm place. Let them stand several hours. In which 
case is the pink color changed most? In which least? If it 
is the organic matter that changes the potassium permanganate, 
which water has the most of it? 

6. Hardness of Water. Put a small piece of a white soap, 
such as Ivory, Pearl, or Fairy soap, into a test tube half full of 
distilled water. Close the tube with your thumb, and shake it 
vigorously for 30 seconds. Then let it stand for 5 minutes. 

Do the same with a test tube half full of hydrant or well 
water, and with one half full of a very hard water. Make the 
very hard water by shaking some powdered calcium sulphate 
(gypsum or plaster of Paris) with water and then filtering the 
solution. Compare the results in the 3 tubes; what differences 
do you see? Which forms the best and most lasting lather or 
suds? Which leaves a scum? If the ability to form a lasting 
suds is a test for a good laundry water, which of the 3 tried is 
the best? Which water would waste the most soap? Do you 
think the scum would be a good thing for the clothing washed? 

EXERCISE 31 
FILTERING AND PRECIPITATING 

Apparatus and Materials. Fine sand, salt, funnel, filter paper, 
watch glass or glass plate, cup of boiling water, potassium dichromate 
solution, solution of lead nitrate or of lead acetate (sugar of lead). 

a. Mix thoroughly half a teaspoonful of fine sand with the 
same amount of powdered salt. Put the mixture into a dish, 
and add to it half a test tube full of hot water. 

Make a filter as shown in Fig. 68, 84, of the text. Fold the 



34 LABORATORY EXERCISES 

circular filter through the middle, and then fold each half. 
Press the folded edges between the thumb and forefinger, but 
not between the nails. Open the filter so that it forms an in- 
verted cone, and fit the cone exactly into the funnel. Hold the 
filter in the funnel, wet it with water, and press it carefully 
against the sides of the funnel. 

Stir the mixture of sand, salt, and Water, and pour the solid 
and liquid together upon the filter. Catch the part that runs 
through (the filtrate) in a dish, and evaporate some of it on a 
watch glass or a glass plate over a cup of boiling water (refer to 
Exercise 29, c). What substance do you obtain? 

b. To 2 cu. cm. of a solution of potassium dichromate add 
twice its volume of a solution of lead nitrate or of lead acetate 
(" sugar of lead")- What happens? Let the solution stand; 
what settles out? 

An insoluble solid that is formed by the mixing of solutions is 
called a precipitate. What color has the precipitate in this case? 
Filter it off, spread out the filter paper, and let it dry. The 
powder consists of " chrome yellow," used in the making of 
certain yellow paints. Evaporate the filtrate; it contains 
"niter," or "saltpeter." 

What is the color of the precipitate formed when carbon 
dioxide is mixed with lime water? Refer to Exercise 15, a. 



EXERCISE 32 
CRYSTALS 

Apparatus and Materials. Powdered alum, beaker or cup, water, 
burner. 

a. Put 10 cu. cm. (about 2 teaspoonfuls) of powdered alum 
into a beaker or cup, and add 20 cu. cm. of water to it. Stir 
the mixture for several minutes. Does some alum dissolve? 



HYDROGEN 35 

Does all dissolve? What evidence is there that you now have 
a saturated solution? 

Heat the dish, and stir the alum and water until the solution 
nearly boils. What happens? Set the solution aside to cool 
slowly. Examine the crystals that are formed; do they have 
any regular form? Ask whether you are to save the alum. 

What was the shape of the salt crystals formed in Exercise 
8, d? 

EXERCISE 33 
DOES THE TEMPERATURE CHANGE DURING SOLUTION? 

Apparatus and Materials. Thermometer, beaker or cup, water, 
ammonium chloride (sal ammoniac), watch glass or glass plate. 

a. Get the temperature of 10 cu. cm. of water in a beaker or 
cup. Hold the dish by the edge, so that your hand will not 
warm the water. Then mix with the water a teaspoonful 
(about 5 cu. cm.) of ammonium chloride (sal ammoniac), and 
stir the mixture with the thermometer. Have the thermometer 
bulb immersed, and hold the dish by the edge, as before. What 
change of temperature is there? 

6. Pour a few drops of the sal ammoniac solution on a watch 
glass or a glass plate, and let it evaporate slowly, without 
applying heat. What form have the crystals? Draw a sketch 
of some of them. 

Ask what you are to do with the sal ammoniac solution. 

EXERCISE 34 
HYDROGEN 

Apparatus and Materials. Small, wide-mouth bottle or a test tube, 
large bottle or fruit jar, a drinking glass, dilute sulphuric acid, granu- 
lated zinc, copper sulphate solution, splinter, kettle or pail of cold 
water, burner. 




36 LABORATORY EXERCISES 

a. Preparation and Properties. Prepare hydrogen in a 
small, wide-mouth bottle, as shown in Fig. 17. The bottle 
contains about 5 cu. cm. of granulated zinc and about 10 
cu. cm. of dilute sulphuric acid. If these substances do not 
act vigorously, add to them about half a teaspoonful of copper 

sulphate solution. Over the small bottle in- 
vert a larger bottle (pint fruit jar); the 
hydrogen displaces the air. A test tube may 
be used instead of the small bottle. 

After some minutes remove the larger 
bottle, keeping its mouth downward, and 
bring to its mouth a long, burning splinter. 
Does the gas take fire? Where? Push the 
splinter up into the jar of hydrogen, and 
hold it steady for a minute or two. Does the 

splinter burn in the hydrogen? Where does it take fire? Why? 
From the method used in collecting hydrogen do you think 

the gas is heavier, or lighter, than air? 

b. Burning of Hydrogen. Light the hydrogen coming out 
of the small bottle or test tube. What is the color of its flame? 
If you cannot see the flame, find out if it is there by holding your 
hand over it. Invert a cold glass or bottle over the flame. 
What is deposited? 

Set a tin cup or beaker of cold water over a gas burner. What 
is deposited on the bottom and sides? Where does it come 
from? What substance must be present in illuminating gas? 
Why does the liquid cease to be deposited after a while? 

EXERCISE 35 
HYDROCHLORIC ACID AND AMMONIA WATER 

Apparatus and Materials. Wide-mouth bottle or drinking glass, 
glass plate, concentrated hydrochloric acid and ammonia water, red 
and blue litmus paper, filter paper or blotting paper. 



CHLORINE 37 

a. Open a bottle of concentrated hydrochloric acid, and blow 
your breath over it; your mouth should be wide open. What 
happens? The cloud or fog is composed of the moisture of 
your breath and the gas that comes from the hydrochloric acid 
of the bottle. Hold a piece of moist blue litmus paper over the 
mouth of the bottle, and state the result. 

b. Open a bottle of concentrated ammonia water, and get its 
odor. Hold a piece of moist red litmus paper in the gas (am- 
monia) that comes out of the bottle; result? 

c. Wet a small strip of paper, such as blotting paper or filter 
paper, with ammonia water, and hold it over the mouth of a 
wide-mouth bottle into which you have poured a few drops of 
concentrated hydrochloric acid. Result? The product is a 
solid (ammonium chloride or sal ammoniac). 

Wet one side of a plate of glass with ammonia water, and lay 
the glass, wet side down, over the bottle containing the few 
drops of hydrochloric acid. Let the apparatus stand for some 
time, and state the result. 

EXERCISE 36 
CHLORINE 

Apparatus and Materials. Wide-mouth bottle, glass plate, man- 
ganese dioxide, concentrated hydrochloric acid, litmus paper, colored 
cloth, paper with ink writing, green leaves. 

NOTE: Chlorine is a dangerous gas to inhale in any con- 
siderable amount, and should be made only under a fume 
chamber or by an open window with an outgoing draft. The 
window does very well. Probably it will be best for the teacher 
or a few students to make a bottle of the gas and to show it 
to the class. If you have breathed too much chlorine, smell 
cautiously of the bottle of ammonia water. 

a. Into a wide-mouth bottle (Fig. 18) put about half a 



38 LABORATORY EXERCISES 

teaspoonful of powdered manganese dioxide and about 2 tea- 
spoonfuls of concentrated hydrochloric acid. Usually the gas 
is formed at once; if it should come off slowly, set the bottle in a 
pail of warm water. What is the color of the gas? Wave a 
little toward your nose, and smell of it cautiously. 
What is its odor? 

6. Hang in the bottle of the gas a piece of moist 
litmus paper (either color), a piece of moist colored 
cloth (such as cheap, red cheesecloth), a piece. of 
paper with ink writing upon it, and a small bundle 
of green leaves, such as grass or parsley. What 



FIG. is. happens to them? Leave them some time if the 
changes are slow. 

Remove the cover of the bottle for a moment, and put a 
burning match into the gas. Does the gas burn? Does the 
splinter continue to burn? 

EXERCISE 37 
SULPHUR 

Apparatus and Materials. Wide-mouth bottle, or fruit jar, with 
cardboard cover; evaporating dish or watch glass, test tube holder; 
combustion spoon and test tube (for a way of making these out of tin, 
see Introduction); sulphur, powdered iron, dilute hydrochloric acid, 
red litmus paper, grass, red rose or carnation petal. 

a. Sulphur Dioxide. In a wide-mouth bottle or fruit jar 
burn some sulphur. You will need a long-handled spoon 
(combustion spoon) and a cardboard cover with a hole for the 
spoon handle. Light the sulphur in a flame before putting it 
into the bottle of air. Let the sulphur burn as long as it will. 
Why does it finally stop burning? 

Wave a little of the gas toward the nose, and learn its odor. 
Into the bottle (or jar) of gas put a piece of moist red litmus and 



CHARRING OF CARBON COMPOUNDS 39 

a small bundle of green leaves, such as grass. If you have it, 
put in also a petal from a red rose or a red carnation. What 
is the effect on each of these? 

b. Iron and Sulphur. On a clean paper mix thoroughly a 
teaspoonful of powdered sulphur and half as much powdered 
iron or fine iron filings. Put the mixture into a test tube, hold 
the test tube by a wire holder, if possible, and heat the bottom 
of the test tube red hot. The heating should start a brilliant 
glow, and this should travel through the mixture as the iron 
and sulphur unite to form iron sulphide. Note the appearance 
of the substance when it is cool; you will need to break the test 
tube. 

c. Hydrogen Sulphide. Put a very small lump of the iron 
sulphide into an evaporating dish or watch glass, and add to it 
1 or 2 cu. cm. of dilute hydrochloric acid. Note what happens, 
and learn the dor of the gas (hydrogen sulphide) that is. given 
off. What is it like? 

EXERCISE 38 
CHARRING OF CARBON COMPOUNDS 

Apparatus and Materials. Small iron dish (cake or muffin tin), 
"tin" cover to fit into it (Fig. 19), ring stand, burner or stove; pieces 
of wood, coal, and starch; sugar. 

a. In a small iron dish (Fig. 19) put some small pieces of 
wood (pine is best), and push the cover tightly into the dish. 
The cover should be circular; it may be cut out of a sheet of 
"tin," or the tin of a can. It should fit into the iron dish about 
half way from top to bottom. In the center of the cover have 
a hole of about the diameter of a small , 

pencil. V~ 

Heat the iron dish over a flame or on \ r~ -> 
a hot stove, lighting the gas that escapes FIG. 19. 



40 LABORATORY EXERCISES 

through the hole in the cover. When no more gas comes off, 
remove the dish from the flame, and let it cool. Then take 
off the cover, and examine what remains in the dish. What 
is it? Save it for the present. 

6. Repeat experiment a, using soft coal instead of wood. 

c. Repeat it again, using half a teaspoonful of sugar. 

d. Repeat it again, using a lump of starch. What is the 
residue called in each case? 

EXERCISE 39 
HOW ORES ARE REDUCED TO METALS 

Apparatus and Materials. Small iron dish of Exercise 38, piece of 
wire, powdered charcoal, lead oxide, burner or stove, limewater. 

a. Powder some of your charcoal, or get some powdered 
charcoal from the bottle, and mix half a teaspoonful of it very 
thoroughly with the same volume of powdered lead oxide (it 
is called litharge). Put the mixture in a heap in your iron dish 
(Fig. 19), push in the cover, and heat the dish very hot for about 
10 minutes. While the heating is going on, hold over the hole 
in the cover a drop of limewater. You can hold the limewater 
in a loop made at the end of a piece of wire. 

What happens to the limewater? What gas must be formed 
from lead oxide and charcoal? From what substance does the 
carbon of the charcoal get the oxygen? 

Let the dish remain covered until it is cool; then examine 
its contents. What change has occurred? Do you get any 
evidence of a metal? If necessary, wash away any unused 
charcoal in a stream of water. What is the metal? Try to 
cut it with a knife. 



CARBON DIOXIDE AND FERMENTATION 41 

EXERCISE 40 
CARBON DIOXIDE AND FERMENTATION 

Apparatus and Materials. Bottle with glass-plate cover, drinking 
glass, fruit jar, marble, dilute hydrochloric acid, candle, splinter, lime- 
water, baking soda, washing soda, sour milk, vinegar, cream of tartar, 
baking powder, limestone, shells, old mortar, molasses or brown sugar, 
yeast. 

a. Carbon Dioxide from Carbonates. In a bottle like that 
of Fig. 18, Exercise 36, put some marble and dilute hydrochloric 
acid. What happens? Put a burning splinter into the bottle; 
does it continue to burn? Does the gas burn? 

Put a very short candle into the bottom of a bottle or drink- 
ing glass, light it, and pour upon it the gas formed from the 
marble and acid (see Exercise 15). Do not pour out any of the 
liquid. What is the effect of the gas upon the burning candle? 

6. Treat half a teaspoonful of baking soda with some sour 
milk, and prove that carbon dioxide is formed. Try washing 
soda and vinegar. 

c. In a water glass or beaker mix about % of a teaspoonful 
of baking soda with twice its volume of cream of tartar, and 
then add water to the mixture. Prove that carbon dioxide is 
formed. In the same way treat a teaspoonful of baking powder 
with water, and find what gas is given off. 

d. Treat small lumps of limestone with dilute hydrochloric 
acid, and prove that carbon dioxide is formed. Do the same 
with some broken oyster, clam, or snail shells. Try some old 
mortar in the same way; what gas is given off, and what is the 
residue that does not dissolve? 

e. Fermentation. In a bottle or fruit jar put 50 cu. cm. of 
warm (not hot) water and 10 cu. cm. of molasses or brown 
sugar. Add about 1 cu. cm. of yeast, cover the bottle loosely, 
and set it where it will remain warm. Watch the contents of 



42 LABORATORY EXERCISES 

the bottle, and note what happens. After the action has 
become vigorous, prove that carbon dioxide is being formed. 
After the action has ceased (it may be after several days), bring 
the fermented solution to the instructor, so that he may distill 
it, and may show that it contains alcohol. 



EXERCISE 41 
LIME 

Apparatus and Materials. Small iron dish, test tube, bottle with 
stopper, glass tube, lump of lime, sand, water. 

a. Put a lump of fresh lime, about the size of a walnut, into 
your small iron dish, and add water, a few drops at a time, as 
the lime absorbs it. Do not use an excess of water. If you 
can see no sign of a reaction at first, try warming the dish 
gently. Note how the " slaking" of lime takes place, and 
describe the process. Watch the process of making mortar for 
some building in your neighborhood, and see how lime is slaked 
on a large scale. 

When your lime has ceased to react with water, mix it with 
enough water to form a thick paste. Mix half of this paste 
with clean sand, and lay it aside for a week or two. What 
happens to it? 

Mix the remainder of the paste with more water, stir the 
mixture (we call it "milk of lime"), and pour it into a bottle 
which can be stoppered tightly. Let it stand until it settles, 
or filter some of the milky solution. Prove that the clear 
solution behaves like limewater. You can do this best by 
putting some in a test tube, and blowing your breath slowly 
through a tube reaching into the liquid. 



MAGNETS 43 

EXERCISE 42 
MAGNETS 

Apparatus and Materials. Bar magnet and horseshoe magnet, 
small iron nails or tacks, iron filings, sewing needles, cork, dish of 
water (glass or porcelain), iron "cut" nail or a wire nail, sheet of paper 
or a pane of glass. 

a. Bring one end of a bar magnet or horseshoe magnet near 
some iron nails or tacks; near a needle, a pin, a piece of "tin- 
ware," a piece of copper (a cent). Are all attracted? Try the 
other "pole" of the magnet with the same materials; what are 
the results? 

b. Magnetize a needle by stroking it, from the middle to the 
point, with one end of a magnet. Magnetize a second needle 
by stroking it with the other end of the magnet, also fr.om the 
center to the point. 

Cut two thin, circular slices of cork from a small cork stopper, 
and push each needle through one of the slices, so that the cork 
will make the needle float in a horizontal position. Float the 
two magnetized needles on some water in a porcelain or glass 
dish (not an iron one). 

Find out whether the points of the two needles attract or 
repel each other. The eye ends. The eye end of one and the 
point of another. 

Float a third needle, one that has not been magnetized at 
all, near one of your floating magnets. Does it show repulsion 
for either end of the magnetized needle? 

c. Hold one end of your large magnet over the floating mag- 
net, and account for the movements that take place. From 
the position which the floating magnet takes, and from the way 
in which it acts toward your large magnet, decide which end of 
the large magnet is north-seeking. 

d. Hold a nail near one end of a magnet, as in Fig. 113 of the 



44 LABORATORY EXERCISES 

text. Use an iron "cut" nail if possible; if you use a wire nail, 
you may need to heat it red hot and then to let it cool slowly. 
While the nail is near the magnet, bring it near small tacks or 
iron filings. What is the result? Now hold the magnet farther 
away from the nail, and note what happens. 

e. Place a horseshoe magnet under the middle of a smooth 
piece of writing paper (or a pane of glass) and sprinkle some iron 
filings over the paper. Tap the paper gently, and see how the 
filings arrange themselves. Draw a sketch showing this 
arrangement. Compare it with the arrangement in the case of 
a bar magnet, as shown in the text, Fig. 114, 138. Is the 
influence of a magnet cut off by paper or glass? 



EXERCISE 43 
ELECTRIC CHARGES 

Apparatus and Materials. Glass rod or a slender bottle, silk pad, 
silk thread, cork or pith, sealing wax, rubber ruler or comb, flannel 
pad or fur muff. 

a. Hold a clean, dry glass rod (or a slender bottle) by one 
end, and rub the other end vigorously with a pad of silk cloth. 
Bring your knuckle near the rubbed part of the glass, but do 
not let it touch the glass. What occurs? Do the same with 
the rubbed part of the silk pad, and tell what happens. 

6. Make an " electric pendulum" by attaching a silk thread 
to a piece of dry cork about 5 mm. in diameter. Instead of 
cork you can use the pith found inside the stem of a burdock. 

Suspend the pendulum from a ring stand, a shelf, or a bracket; 
then rub the glass and silk together, and hold the glass near 
the pendulum. What happens at first? What further change 
takes place? Now hold your hand near the charged pendulum; 
what happens? 



A SIMPLE ELECTRIC CELL 45 

Hold the pendulum in your hand for a second or two, to dis- 
charge it; then hold near the uncharged pendulum the rubbed 
silk pad. Give all the results. 

c. Rub a stick of sealing wax, or a rubber ruler or comb, with 
a piece of woolen goods, such as flannel. Bring the sealing wax 
(or rubber) near an uncharged pendulum, and compare the 
results with those that took place when glass was used. Also 
try the action between the rubbed part of the flannel and the 
uncharged cork. Give all the results. 

d. Charge two electric pendulums from a rubbed glass rod, 
and hold them near each other, as in Fig. 119, 143, of the text. 
What happens? 

e. On a cold, dry evening put on some heelless slippers, 
and shuffle your feet vigorously, several times, across a rug or 
carpet. In this way your body becomes charged; so does the 
rug or carpet. Now hold your finger near a metallic object, 
such as a door knob or a chandelier. Describe what takes 
place. 

On the same kind of a night comb your hair vigorously with 
a rubber comb, and prove that the comb becomes charged. 
Do the combed hairs show any sign of repelling one another? 
Why should they? 

/. With a silk handkerchief, a flannel cloth, or a fur muff, rub 
a sheet of smooth paper, and hold the paper near the wall. 
Tell what happens, and why? 

EXERCISE 44 
A SIMPLE ELECTRIC CELL 

Apparatus and Materials. Strips of sheet zinc and sheet copper, 
pieces of copper wire, block of wood, tacks, drinking glass or jelly 
glass, compass or floating magnet, dilute sulphuric acid, saturated 
solution of potassium dichromate. 



46 



LABORATORY EXERCISES 




FIG. 20. 



a. Prepare a strip of sheet zinc and one of sheet copper, each 
about 3 x 10 cm., and make a small hole near one end of each 
strip. Through each hole put one end of a piece of copper wire 
about 20 cm. (8 in.) long, bend the part that is through the 
hole, and with a hammer flatten the wire tightly against the 
strip. Then tack the strips of metal on opposite 
sides of a block of wood (Fig. 20) long enough 
to reach across the glass. 

b. Half fill the glass with dilute sulphuric acid, 
and put the free ends of the two metal strips into 
it. Note what happens. From which metal do 
bubbles appear to rise? Touch the tips of the 
copper wires, held a little distance apart, to the 
tip of the tongue. What evidence do you get 
that a current is traveling through the wires? 

c. Join the free ends of the two wires, and place them over a 
compass or a floating magnetized needle (c/. Exercise 42). 
What is. the result? 

d. If your simple cell is too weak to give good results, put 
into the dilute sulphuric acid about 10 cu. cm. of a saturated 
solution of potassium dichromate, and try the experiments 
again. What are the results now? 

EXERCISE 45 
THE SAL AMMONIAC CELL 

Apparatus and Materials. A sal ammoniac cell, ready to set up^. 
wooden paddle, battery that operates house doorbells. 

a. Examine the construction of a "sal ammoniac" cell. 
The common form is also called a "carbon cylinder" cell. If 
the cell is not ready to use, set it up according to the directions 
on the jar. Usually about 150 g. (5 ounces) of solid am- 
monium chloride are used. This is mixed with water, and 



ELECTROMAGNETS 



47 



the water is stirred until the solid is dissolved. A clean wooden 
stick, whittled into the form of a paddle, makes a good stirring 
rod. The upper level of the solution should be at least 5 cm. 
(2 in.) below the top of the jar before the zinc and carbon are 
put in. 

6. Find out where in your house the battery for the electric 
bell is placed, and get help, if necessary, to take it out, so that 
you can examine it. Describe it in your notes, giving the 
commercial name, the name of the manufacturer, etc. 

How much did your house battery cost per cell? Find out 
how long the stick of zinc lasts, and how much a new one costs. 
What is the "life" of the sal ammoniac solution, and how much 
does a new charge of sal ammoniac cost? 

c. If your doorbell is operated by "dry" cells, get all the 
data regarding them, and write 

the data in your notes. 

d. If your doorbell is operated 
by a battery of two or more cells, 
notice how they are connected. 
If the carbon of one cell is con- 
nected with the zinc of the next 



Cell, as in Fig. 134, 159, Of the Three Cells Connected "In Parallel" 

text, the cells are said to be con- 
nected in series. If all the carbons are connected with one 
wire, and all the zincs with the other wire, as in Fig. 21, the 
cells are said to be connected in parallel, or abreast. 



EXERCISE 46 
... ELECTROMAGNETS 

Apparatus and Materials. Sal ammoniac cell, insulated wires, 
magnetized needle or compass, soft iron bar or wire nail, for a core; 
iron filings, tacks, and nails. 



48 LABORATORY EXERCISES 

a. We have already tested the effect of a wire carrying a 
current upon the magnetized needle or compass. Try it again 
with the sal ammoniac cell, but use covered (" insulated") 
wire. 

b. Coil the insulated wire around a thick pencil, giving it 
about 10 turns. Hold the coil of wire, with a current flowing 
through it, in some iron filings or small tacks. Do any cling 
to the coil? 

c. Into the coil of wire put a bar of soft iron. A large wire 
nail will do, if you first heat it red hot, and then let it cool 
slowly. Bring the soft iron "core" of this "electromagnet" 
near some iron filings or tacks. Are more, or less, picked up than 
when the coil alone was used? Now "break the circuit" by 
disconnecting one of the wires from the cell, or by separating 
the wires that connect the zinc and the carbon. What takes 
place? 

d. Again coil the insulated connecting wire around a pencil, 
winding it in about 50 turns, or as many as the length of the 
wire permits. Instead of doing this you can use a coil, already 
prepared and having a large number of turns. Into the coil 
put the soft iron core, and let the current flow. How does the 
ability of the electromagnet to pick up iron nails, etc., compare 
with its strength when the coil is small? 

What, then, is the advantage gained by the use of a coil of 
many turns? 

EXERCISE 47 
SHADOWS 

Apparatus and Materials. Ordinary candle and "birthday" candle, 
each about 8 cm. (3 in.) high, two cardboard squares, upright object, 
such as two spools; kerosene or electric lamp. 

a. Take an ordinary candle and a small "birthday" candle, 
each about 8 cm. (3 in.) high, and fasten them to cardboard 



BRIGHTNESS CHANGES WITH DISTANCE 49 

squares about 6 cm. on a side. You can do this by heating the 
bottom of the candle with a burning match until a little of the 
wax has melted and dropped upon the middle of the cardboard. 
Then press the candle against the cardboard until the wax has 
hardened. 

In a room that is dark, light the larger candle, and place near 
it some opaque, upright object, such as two spools of thread 
one on top of the other. Have both the candle and the spools 
on a piece of white paper. Examine the shadow behind the 
spools, and see that it has two parts, one (the umbra) much 
darker than the other (the penumbra). Draw a sketch of the 
shadow, labeling each part, but not shading it. 

b. Carry out the same test with the small candle; then try 
a larger source of light, such as a kerosene or electric lamp. 
The lamp must be reasonably near the spools. Draw the 
shape and size of the umbra and penumbra in each case, and 
compare them. 

c. Now put the two candles as close together as possible, and 
place the spools near them. 

Note how the shadows, and their parts, cross one another. 
Draw these parts, labeling them. Then slowly move the 
candles apart, noting the effect upon the umbra and penumbra. 
What is the effect of a large flame, or of separate flames, upon 
the size of the penumbra? 

EXERCISE 48 
BRIGHTNESS CHANGES WITH DISTANCE 

Apparatus and Materials. Cardboard square 4 cm. on a side, sheet 
of paper, metric rule, checkerboard, "birthday" candle. 

a. Out of cardboard cut a square piece 4 cm. on a side; then 
draw on a piece of white paper a large square divided into 16 



50 LABORATORY EXERCISES 

squares each 4 cm. on a side. Darken the room, and use a 
small " birthday" candle as the source of light. 

Hold the small square upright, 10 cm. from the candle flame, 
and hold the ruled paper beyond it, and at such a distance that 
the shadow of the small square just covers 4 of the squares 
on the ruled paper. Measure the distance of the ruled paper 
from the flame, and compare it with the distance of the small 
square from the flame. Give the results. 

6. Hold the cardboard square as before, 10 cm. from the 
flame, and hold the ruled paper so that the shadow of the small 
square covers 9 squares on the ruled paper. Compare the 
distances as before. 

Again change the position of the ruled paper so that all 16 of 
the squares are covered by the shadow of the small square. 
What is the distance between the ruled paper and the candle 
now? 

c. How many squares are there on a checkerboard? If you 
were to cut a cardboard square having the size of one of the 
checkerboard squares, and were to hold it upright, 10 cm. from 
the candle flame, how far from the candle would the checker- 
board need to be so that the shadow of the single square could 
cover all the squares of the board? 

EXERCISE 49 
CANDLE POWER 

Apparatus and Materials. Large and small candles of Exercise 47, 
two spools of thread, white paper, lamp or electric bulb, metric rule. 

a. In a dark room use again the two candles, the spools of 
thread, and the white paper of Exercise 47. Place the spools 
(one upon the other) between the two candles, and note whether 
the two shadows are equally dark. If not, shift the spools until 
this is the case. Then measure the distance from the spools to 



MIRRORS 51 

each flame, and square this distance; that is, multiply it by itself. 
Now divide the square of the distance of the larger candle by 
the square of the distance of the smaller candle. Suppose the 
result is 3.5. This would mean that the larger candle has 3.5 
times as great an illuminating power as the smaller candle. 
What result do you get? 

b. Now compare the illuminating power of a lamp, or of an 
electric bulb, with that of the large candle. Instead of the 
spools, you can use an upright pencil, and instead of putting it 
between the two sources of light, you can put it to one side, as 
in Fig. 145, 171, of the text. What is the "candle power" of 
the lamp or bulb? 

EXERCISE 50 
MIRRORS 

Apparatus and Materials. Mirror (vertical), two hand mirrors, 
pencil, plate glass or thick window glass, bottle of water, small candle, 
silver spoon. 

a. Before a vertical mirror hold an open book, with the pages 
toward the mirror. How are the letters apparently altered by 
the reflection? 

b. Lay a mirror, such as a hand glass, on the table before you, 
and set an open, upright book behind the mirror. How does the 
image of the letters differ from the letters themselves? 

c. With a mirror lying flat on the table before you, take a 
second mirror in both your hands and revolve the mirror slowly, 
so that first its face and then its back are turned toward you. 
By changing your distance from the mirror you will find a 
position in which you can see images of yourself, at one time 
upright, at another, upside down. Objects behind the mirror 
will also form images in both upright and inverted positions. 
You can also get a large number of images of yourself at one 



52 LABORATORY EXERCISES 

time, because not only the object (yourself) is reflected, but 
your image in one mirror is reflected by the other mirror. 

What phenomenon do you see when you stand in a room that 
has vertical mirrors on opposite walls? 

d. On a mirror put a speck of soap or ink, and look at the 
spot from one side. How many specks appear? Why? How 
can you use the distance between the speck and its image to 
get an idea as to the thickness of the glass of the mirror? 

e. Hold an object, such as a pencil, near, but not touching, a 
mirror, and look at it from one side. The mirror should not be 
in too bright a light. You should see 3 images of the object. 
Remembering that the glass has thickness, and that the front, 
as well as the back, can reflect light, tell why there are so many 
images. 

/. With a piece of plate glass or thick window glass carry out 
the experiment shown in Fig. 149, 175, of the text. 

g. Curved Mirrors. Use a bright silver spoon (a circular 
one, if you can get it) as a curved mirror. The bowl will be a 
concave mirror; the back of the bowl, a convex mirror. Darken 
the room, and hold a small candle flame between the bowl of the 
spoon and your eyes. The image of the flame will be in front 
of the spoon, and inverted. If you turn the convex side of the 
spoon bowl toward you, and hold the flame between your eyes 
and the spoon, the image of the flame will appear back of the 
spoon, and right side up. 

EXERCISE 51 
REFRACTION OF LIGHT 

Apparatus and Materials. Thick glass, cup, coin, water, glass lens, 
paper, match. 

a. Lay a piece of thick window glass, or of plate glass, over a 
straight pencil mark, so that the mark projects beyond the 



OF WHAT IS WHITE LIGHT COMPOSED? 53 

edge of the glass. Note that if you look vertically through the 
glass, the line appears unchanged, but if you look at the line 
obliquely, it appears to be broken at the edge of the glass. 
Explain the phenomenon. 

b. In a cup place a coin. Raise the cup so that the coin just 
disappears from view, behind the side of the cup. Now hold 
both the cup and your eyes steady, and pour water slowly into 
the cup. Note how the coin comes into view, and explain why. 

c. Refraction by a Lens. Get a glass lens with two convex 
faces, or with one plane and one convex face. You can use a 
magnifying glass, a reading glass, or the lens from a discarded 
bicycle lamp or " flashlight." Look through the lens at print, 
cloth, etc., holding the glass near the object. Note that the 
object seems enlarged. Is the image reversed in any way? 

Now move the lens farther from the object, and the parts of 
the object will appear reversed. What must have happened to 
the rays of light when the image is a reversed one? See Fig. 
141, 168, of the text. 

d. Burning Glass. Let sunlight pass through your lens, and 
hold the lens at such a distance from the back of your hand that 
the rays are brought together in one tiny, bright spot (a focus). 
Do you get any evidence that the sunlight brought together 
contains or produces heat? See if you can ignite paper, or a 
match, by holding it at the focus of your burning lens. 

EXERCISE 52 
OF WHAT IS WHITE LIGHT COMPOSED? 

Apparatus and Materials. A glass prism or a substitute, color top 
(see below) , colored, glazed paper such as is used for covering boxes, 
tacks or thumb tacks. 

a. Decomposing White Light into its Colors. Get some 
thick, transparent glass object with glass surfaces that are not 




54 LABORATORY EXERCISES 

parallel. A 3-sided prism is the best thing to use, but other 
objects, such as a chandelier pendant, a cut-glass bowl, or a 
many-sided perfume bottle made of thick glass, will do. On 
a sunny day darken a room almost completely; then let a beam 
of sunshine enter through a crack around the window shade. 
Place the prism, or its substitute, in the path of the sunbeam, so 

that the spectrum of " rainbow" 
colors will be thrown upon a 
sheet of white paper placed on 
the wall, the floor, or on a table. 
Give the names of the colors in 
their order. 

6. Mixing of Colored Light. 
In this experiment you will need 
a " color top." You can buy one 
FIG 22 at a toy store, or ypu can make 

one as follows (Fig. 22) : 

Out of stiff cardboard cut a circle 8 cm. in diameter (3 in.), and in 
the center make a square hole about 4 mm. on a side. Make a 
peg and handle for the top out of a soft-wood stick about 5 cm. long and 
6 mm. thick. Let the "peg" end remain as thick as the original 
stick, but cut down the rest of the stick slightly, so that the cardboard 
can slip down to a "stop" 1.5 cm. from the peg, but no closer. Have 
the peg smoothly rounded, so that the top will spin evenly. The part 
that is to hold the cardboard circle should be square in cross section, 
so that the circle cannot turn on the stick. Round off the upper part 
of the stick (the handle). The circle should be slipped over the handle 
until it comes to the "stop," above the peg. By twisting the handle 
between your thumb and second finger you can spin the top. 

c. Out of sheets of colored paper cut circles having the size 
of the cardboard one. Use violet, blue, green, yellow, red, and 
black paper. Make a round hole in the center of each circle, 
and cut a slit from circumference to center. Take first a yellow 



HOW COLOR IS AFFECTED BY THE KIND OF LIGHT 55 

circle and a blue one. By slipping one circle through the slit 
of the other you can get portions of each color to show. Move 
the two circles over each other so that % of the circle is blue 
and M is yellow. Slip the combination circle on the top, and 
fasten it to the cardboard by means of tiny tacks or thumb 
tacks. Instead of tacks you can use a drop or two of paste. 
Then spin the top. What color do you get? Remember that 
gray is poorly illuminated white. 

d. Try a combination yellow-red circle; what is its color? A 
red-blue circle. 

Make a circle out of the 3 colors : red, green, and blue, each of 
them ^ of the circle. What color do they give? 

e. Try a black disk with a yellow one, using several different 
proportions of the colors. Try black and red and black and 
green, giving the results. 

EXERCISE 53 
HOW COLOR IS AFFECTED BY THE KIND OF LIGHT 

Apparatus and Materials. Strip of blotting paper or asbestos paper, 
saturated salt solution, Bunsen or alcohol burner, colored papers of 
Exercise 52, lamp with a red globe (or paper soaked in strontium 
chloride solution). 

a. Soak a strip of blotting paper or asbestos paper in a 
saturated salt solution, and dry it on a radiator. Have the 
room dark, and hold the prepared paper in a Bunsen or alcohol 
flame. What is the color of the light given by the flame? 
Examine the colored papers of Exercise 52 in this "sodium" 
light. What color has each one? 

6. Examine the colored papers in a red light. Get this 
light from a lamp or lantern with a red globe, or cover a globe 
with red crepe paper. What is the apparent color of each 
paper? 



56 LABORATORY EXERCISES 

You can get a crimson light from a piece of blotting or 
asbestos paper that has been soaked in a solution of strontium 
chloride and then dried. 

c. In order that a color may appear red, what kind of rays 
must be" in the light that illuminates it? What rays must a 
light contain if we are to see an object as yellow? Why do 
objects have these colors in sunlight? Why do colors appear 
unnatural by electric light? 

EXERCISE 54 
HOW SOUND IS MADE AND CARRIED 

Apparatus and Materials. Table bell or doorbell, tuning fork or 
table fork, newspaper, watch, pillow, room with steam pipes or water 
pipes, wooden board. 

a. While a table bell or doorbell is ringing, touch the bell 
lightly with your finger. What proof have you that the bell 
is vibrating? 

b. Strike a tuning fork lightly against the edge of a table, and 
hold your finger against the fork. Account for the result. A 
table fork can be used in the same way. Hold the fork lightly 
by the handle while you strike the back of the prongs against 
a table or chair, and then bring the vibrating fork near the top 
of some loose paper, such as a partly folded newspaper. What 
is the result, and why? 

c. Lay a watch upon a pillow, at some distance from you, 
say, at the farther end of a table. Note whether you can hear 
the watch, and how loud the ticking is. Then lay the watch, 
at the same distance, upon the bare table, and compare results. 

d. Have some one scratch with a pin, or tap with a pencil, at 
one end of a steam or water pipe, and put your ear close to the 
other end of the pipe. Can you hear the sound? Can you 



LEVERS 57 

hear it as well when your ear is away from the pipe? What 
conclusion can you draw from this fact? 

Try the same experiment with a long, wooden board. 

EXERCISE 55 
HOW SOUNDS ARE STRENGTHENED 

Apparatus and Materials. Wide-mouth bottle, tuning fork or 
table fork, metric rule, water. 

a. Into a wide-mouth bottle, such as a milk bottle or fruit 
jar, pour a little water, and hold over the mouth of the bottle 
(near it, but not touching) the prongs of a vibrating tuning fork 
or table fork. If the sound produced by the fork does not 
increase in loudness, add more water, so that the depth of the 
water will be increased about 1 cm., and set the fork in vibra- 
tion once more. Do this again and again until the sound is 
reinforced, or strengthened, so that you can hear it very plainly. 
For a common, Rogers Brothers', plated table fork the rein- 
forcement was found to be loudest when the water was 9 cm. 
from the top of the bottle. That is to say, the vibrating air 
column was 9 cm. high. What is the length for your fork? 

6. Try another tuning fork or table fork. Strike it, and note 
whether its pitch is higher or lower than that of the first fork. 
If it is lower, make the air column longer; that is, take out some 
of the water. If the pitch is higher, make the air column 
shorter. Get the length of the air column in this case also. 

The reinforcement of sound by means of a second vibrating 
material (here it is air) is called resonance. 

EXERCISE 56 
LEVERS 

Apparatus and Materials. Strip of wood for lever, fulcrum, books, 
a weight, such as a flat stone. 



58 



LABORATORY EXERCISES 



V 



FIG. 23. 



a. For this exercise you need a strip of dry wood about 
5 cm. (2 in.) wide and 45 cm. (18 in.) long. Make a triangular 
block for a fulcrum (a spool laid on its side will do), and lay 

^ --^ A the strip of wood 

(the lever) over the 
fulcrum, as in Fig. 
. 23, A. Put a book 
near one end of the 

B lever, and push 

i A ' downward at the op- 

^ ^ posite end. Change 

the fulcrum so that 

I ^ its positions vary 

-3 from almost under 
the book to almost 
under your hand. 
When is it easiest to lift the book? When is it hardest? 
Such a lever is of the first class. Where is the fulcrum placed 
as regards the weight (the book) and the place where the power 
(your hand) is applied? 

6. Vary the experiment by hanging the book in a sling of 
stout twine (Fig. 24) and putting the loop of the string over the 
lever, near one end. Use the back of a chair as the fulcrum. 
Hang another book of the same weight at the opposite end of 
the lever. 

Where must the fulcrum be 
placed so that the two arms of 
the lever, with their loads, will 
balance each other? 

Now put two books at one end 
and one at the other. About how 
far from the end having one book 
must you place the fulcrum? From FIG. 24. 






1 \ 






1 I 






1 






1 






i ; 






i 






i \ 





TOOLS BASED ON THE LEVER 59 

the end having two books? Compare the lengths of these two 
arms of the lever. 

Finally put three books at one end and one at the other, and 
compare the lengths of the two arms of the lever. 

Is it true in the first case that the weight arm multiplied by 
its load is equal to the power arm multiplied by its load; that 
is, that the weight arm multiplied by its number of books is 
equal to the power arm multiplied by its number of books? 

Is it true in the second case? In the third? 

c. Make a second-class lever as in Fig. 23, B. Put the book 
near the fulcrum, and lift upward at the end having the arrow. 
Move the book toward the hand, and note how much effort 
you need to put forth to lift the power arm. Where is the book 
when the lifting is most easy? When it is most hard? What 
is the greatest force you must exert in lifting a weight with a 
second-class lever? 

d. Make a third-class lever as in Fig. 23, C, using your left 
hand as a loose fulcrum to keep the fulcrum end from slipping 
out of place. Put the book on the other end of the lever, and 
with your right hand lift upward at the left of the book. Try 
lifting upward at several places, each one a little nearer the 
fulcrum. What are the results? At which part of the lever is 
the lifting most easy? What is the smallest weight you must 
lift in raising a book by means of a third-class lever? 

e. Use a book cover as a lever, placing a weight upon it. 
Find where the weight is when the greatest effort is needed to 
lift it. Where is the weight when the least effort is needed? 
To what class of levers does the book cover belong? 

EXERCISE 57 
TOOLS BASED ON THE LEVER 

Apparatus. Jackknife, scissors or shears, can openers, hammer, 
board, nail, nail extractor. 



60 LABORATORY EXERCISES 

a. Open the blade of a jackknife and show that the blade 
itself is a lever. What is the force to be overcome in opening 
the knife? If the springs were equally strong, and the dis- 
tances from the rivets (fulcrums) to the springs were equal, 
which blade could be opened more easily, a long one or a short 
one? 

6. With a pair of scissors or shears try to cut a match stick. 
Where must you place the stick in order to cut it most easily? 
Why? 

c. Examine several of the " openers" used for opening "tin" 
cans, and find one that is a lever of the first class. Describe it. 
Find one that is of the second class. Describe it. 

What kind of a lever is a full suit case when you are trying to 
close it? 

d. Suppose that you stand on the outside of a closed door, 
and that your brother is on the inside trying to hold it shut. 
If you push against the knob, and he against the middle of the 
door, what kind of a lever is the door, so far as you are con- 
cerned? What kind of a one is it so far as he is concerned? 
Suppose he pushes against the knob, where ought you to push 
to get the greatest advantage? 

e. Find out from a carpenter how to drive a nail into a board. 
How should the hammer be held? Why? How should the 
nail be held? Why? Drive the nail partly into the board, then 
draw it out. Find out how to do this properly. 

/. Ask to see the construction and operation of the nail 
extractor used in opening large packing boxes, such as those of 
a dry goods store. Describe it. 

EXERCISE 58 
PULLEYS 

Apparatus and Materials. Pulleys or casters, string or tape, books 
for weights. 



THE INCLINED PLANE 61 

a. Support a pulley as in Fig. 175, 201, of the text, and 
fasten a weight, such as a book, to one string. 

How much force must you exert, pulling downward, to 
lift the book? Prove this by fastening a second book, of 
the same weight as the first, to the free end of the string. Do 
the books balance each other? What is the use of such a 
pulley? 

b. Now try two pulleys, as in Fig. 176 of the text. Do you 
need to exert more, or less, force than the - 

weight of the book? Note carefully how far 
down you must pull the free cord, and how 
far the weight rises. How do the distances 
compare? 

Put two books for the weight, and one on 
the free end of the string. Can the one be 
made to balance the two? Why? 

c. Finally, support two pulleys as shown in 
Fig. 25, this manual. Can one book be made 
to balance two? 

d. If you can get no pulleys for this exercise, use casters, 
such as are put under bureaus and tables. In this case use tape 
for your pulley cord, as this will not slip off so easily as string. 



EXERCISE 59 
THE INCLINED PLANE 

Apparatus and Materials. A board about 3 ft. long (a drawing 
board, moulding board, or ironing board will do for 6), spool, nail to 
fit it, two-pointed tacks, cord or tape, round dowels or spools or a 
cart, books for weights. 

a. Make an inclined plane out of a board about 3 ft. long 
(Fig. 26) . To make the friction small at the edge of the board 




62 



LABORATORY EXERCISES 



a spool is fastened to the board. The axle of the spool may be 
a wire nail that is nearly as large as the hole in the spool. It 
may be fastened to the edge of the board by means of two- 
pointed tacks. 

For the weight (Fig. 27) use a book in a sling, and a cord or 
tape long enough to go over the edge. Under the book place 





FIG. 26. 



FIG. 27. 



two round dowels about 8 cm. (3 in.) long, or use spools. 
Best of all, use a small cart with spools for wheels. 

Make the plane half as high as it is long, and see if one book 
will support two. Then make it H as high as it is long, and see 
if one book can support three. If you use a cart, you must 
make allowance for the weight of the cart. 

b. Simpler Form. Use a drawing board, moulding board, 
or ironing board for the inclined plane. Up the plane roll an 
unopened tin fruit can, such as a can of tomatoes or peaches. 
If the plane is vertical, how much force must you exert? If it 
is half as high as long? If it is Ji as high as long? If it is 
horizontal? 

Find out where you can see an inclined plane in actual use, 
watch the operation, and describe it. 



THE SCREW 63 

EXERCISE 60 

THE SCREW 

Apparatus and Materials. Steel screw, metric rule, board of soft 
wood, hammer, screw driver, carpenter's brace, screw-driver bit. 
For examination: copying press, jackscrew, carpenter's wood screws. 

a. Examine an ordinary steel screw, measure accurately 
the threaded part, and count the number of threads. What is 
the distance between two successive threads? 

b. Force a screw into a piece of soft wood. To do this, first 
give the head of the screw a tap or two with a hammer, so as 
to "start" the screw. Then use a screw driver, giving it a 
few turns. Can you turn the screw with the fingers alone? 
Why? 

c. Find out how far it is around the screw-driver handle 
(circumference) at its thickest part. If the screw driver has 
flat sides, get its greatest thickness (diameter) and multiply 
this by 3y. Compare the circumference of the handle with 
the distance between threads. How far must the hand be 
turned in order to make the screw advance the distance between 
two successive threads? If you exert a force of 1 kg. on the 
circumference of the screw driver, how much do you exert on 
the threads? 

d. Go to a hardware store, and ask to see the different vari- 
eties of screws. Ask for what each kind is used. How are the 
sizes of screws stated? Ask to see a copying press, a jackscrew, 
and carpenters' wood screws, and have their uses explained to 
you. 

e. Examine a carpenter's brace, and put into it the screw- 
driver bit. Use this to drive the screw farther into the wood. 
Can you drive the screw more, or less, easily than with the 
screw driver? Why? 

Find out how large a circle your hand goes through in turning 



64 LABORATORY EXERCISES 

the brace once. How many times as great as the distance 
between threads is the circle "described" by your hand? If 
you exert a force of 1 kg. on the brace, how much do you exert 
on the screw threads? 



EXERCISE 61 
WHEEL AND AXLE 

Apparatus and Materials. Wheel and axle (usual form) or a wheel- 
barrow, cord, tape, books or weights. 

a. Set up a wheel and axle as shown in Fig. 178, 202, of the 
text. Wind the cord about the wheel so that it will unwind at 
the same time that the cord on the axle is wound up. What 
is the diameter of the wheel? Of the axle? How many grams 
tied to the cord that is attached to the wheel will just balance 
100 g. on the cord attached to the axle? If you attach one book 
to the wheel, how many books of the same weight will it support 
on the axle? 

6. Another form of the apparatus can be made out of a 
wheelbarrow. Turn the wheelbarrow upside down, over a box 
or some saw horses if possible, so that the wheel will be at least 
45 cm. (about 18 in.) from the floor. 

A stout cord tied to the inner end of one of the wheel spokes 
is to be wound upon the ' ' hub." The hub serves as the ' ' axle " 
of the apparatus. A tape may be tied to the rim of the wheel, 
so that the free end of the tape is wound up at the same time 
that the cord on the hub is unwound. 

What is the diameter of the wheel? What is the diameter of 
the hub at the place where the cord is attached to it? How 
great a weight, tied to the hub cord, can be supported by 1 kg. 
tied to the wheel tape? Try the experiment, using several 
books of equal weight if you have no metal weights. 



FRICTION 65 

EXERCISE 62 
FRICTION 

Apparatus and Materials. Book, flatirons, spools or dowels, wheel- 
barrow or cart, machine oil, bicycle. 

a. Lay a book upon the table, and push it over the table. 
What force must be overcome? Does the degree of smoothness 
of the book cover and the table have anything to do with the 
force required? Now put some flatirons or other heavy weights 
on the book, and try the experiment again. What is the result? 
Put under the book and its weights four spools, or two round 
dowels (cf. Exercise 59), and try moving the book. Suggest 
why "rolling" friction is less for a given weight than " sliding" 
friction. 

b. Try spinning, as hard as you can, the wheel of a wheel- 
barrow or cart that has not been oiled recently. Count the 
time during which it continues to turn. Now lubricate ("oil") 
the bearings with machine oil, and find for how long the wheel 
continues to turn. Give the cause of any difference that you 
notice. 

c. Why is oil put on "oil stones" that are used for the 
sharpening of cutting tools? Have some one take off a bicycle 
pedal for you, and examine the "ball bearings." Why are they 
used? 

EXERCISE 63 
APPLIED FORMS OF SIMPLE MACHINES 

Apparatus. For examination: bread mixer, egg beater, self- 
sealing fruit jar, ordinary fruit jar, skates, sewing machine, bicycle, 
typewriter, clothes wringer, washing machine, screw eye, " crosscut" 
and "rip" saws. 

a. Examine a bread mixer. How many simple machines can 
you find about it? 



66 LABORATORY EXERCISES 

b. Count the number of cogs in the large wheel of an egg 
beater. In the small wheel to which the beating apparatus is 
attached. How many times does the small wheel revolve while 
the large wheel is turned one revolution? 

c. What kind of a machine is there in the "self-sealing" 
fruit jar? In the ordinary form? In modern ice skates? In 
a door catch ? In a window having window weights? In a win- 
dow fastener? In a key? 

d. Examine carefully a sewing machine, a bicycle, a type- 
writing machine, a clothes wringer, and a washing machine, and 
write down all the simple machines you find in each. 

e. What tool is a screw driver when you use it to take a tack 
out of the floor? To force a screw eye into a board? 

/. Examine a " crosscut" saw, and describe it. Do the 
same for a "rip" saw. What kind of a simple machine is a 
saw? 

EXERCISE 64 
ACIDS 

Apparatus and Materials. Glass or porcelain dishes, test tubes, 
dilute sulphuric, nitric, hydrochloric, and acetic acids; crystals of 
tartaric and citric acids; lemons, grapefruit, oranges, tomatoes, sour 
milk, vinegar, dill pickles, rhubarb; blue litmus paper, ammonia water, 
tea leaves, apple, dry oak leaves, zinc, copper (wire or cent), iron 
(filings or tacks). 

a. Taste of Acids. What is the characteristic taste of 
lemons, grapefruit, oranges, and tomatoes? Of sour milk, 
vinegar, dill pickles, and rhubarb? 

To 5 cu. cm. of water add a few drops of ordinary, dilute 
sulphuric acid, and taste the solution; then spit it out. Save 
the remainder for b. Do the same with a few drops of dilute 
hydrochloric acid; with dilute nitric acid; with acetic acid. 
Give the results. 



ACIDS 67 

Taste a crystal of tartaric acid; one of citric acid. What 
taste have they? What is meant by an acid taste? 

b. Acids and Litmus. Test each of the fruit j uices (at home?) 
and acids of a with blue litmus paper. One piece of litmus 
paper will do, if, after the color has been changed, you restore 
the original color. Do this by dipping the paper into dilute 
ammonia water; then wash off the ammonia water under the 
faucet. If you wish to dry the litmus paper, lay it on a blotter 
or a piece of newspaper. Write down all the results. 

Boil some tea leaves with water, and test the solution with 
blue litmus. Do the same with a piece of an apple; with some 
dry oak leaves. Give the results. 

c. Acids and Metals. We have already tried the action of 
zinc with dilute sulphuric acid (cf. Exercise 34). What gas 
was formed? Try zinc, in a test tube, with dilute hydrochloric 
acid; also iron filings or small tacks with either dilute sulphuric 
or hydrochloric acid. Is the same gas formed? 

To a piece of copper wire, or to a cent, add about 5 cu. cm. of 
dilute nitric acid. Does any reaction take place? Warm the 
acid if necessary. What kind of a gas is formed this time? 
What happens to the copper? What is the color of the solution? 
After a few minutes pour the liquid into another dish, and rinse 
all the acid from the copper. 

d. Acids and Carbonates. The reactions of acids with 
carbonates have already been studied (cf. Exercise 40). What 
happens when soda or marble is treated with a dilute acid? 

Name four ways in which we have tested for an acid. 

EXERCISE 65 
BASES, OR ALKALIES 

Apparatus and Materials. Glass or porcelain dishes, solid potas- 
sium hydroxide or sodium hydroxide, red litmus paper, dilute acetic 



68 LABORATORY EXERCISES 

acid, ammonia water, limewater, washing soda, laundry soap, "Gold 
Dust," wood ashes, dilute hydrochloric acid. 

a. Examine some solid potassium hydroxide or sodium 
hydroxide; then dissolve a piece the size of a bean in about 3 
cu. cm. of water. Rub a little of this solution between your 
fingers. How does it feel? Dilute the solution with more 
water, and test it with red litmus paper. You can use the piece 
of blue litmus of the last exercise, if you will first dip it into 
dilute acetic acid. Wash off the excess of acid with running 
water. How does the alkali affect red litmus? 

6. Test the following with red litmus: ammonia water 
(cf. Exercise 64), limewater, solution of washing soda. Also 
test a piece of some laundry soap, or its solution, and some wet 
"Gold Dust." What takes place? 

c. Get some wood ashes (or burn some wood to ashes), treat 
them with water, and filter the solution. Test the filtrate with 
red litmus. What is the result? 

d. Put upon a small piece of potassium hydroxide or sodium 
hydroxide a drop of dilute hydrochloric acid. Is there much 
effervescence? Let a similar piece stand in the air for a day; 
then add a drop of acid. What is the result? What has the 
hydroxide probably taken up from the air? What happens to 
lime that is exposed to the air? Why does mortar become hard? 
See 132, text. 

EXERCISE 66 
NEUTRALIZING A BASE BY AN ACID 

Apparatus and Materials. Glass or porcelain dish, solid sodium 
hydroxide, litmus paper, dilute and concentrated hydrochloric acid, 
lemon, limewater, filter paper and funnel, black or blue woolen cloth, 
ammonia water, baking soda. 

a. In a glass or porcelain dish dissolve a lump of sodium 
hydroxide the size of a bean in about 10 cu. cm. of water. 



SOAP AND SOAP MAKING 69 

Save a few drops of it. Into the greater portion put a small 
piece of litmus paper (either color; why?); then add dilute 
hydrochloric acid drop by drop, stirring the solution after every 
drop, until the litmus is just barely pink (lavender). If you 
get too much acid, add a drop more of sodium hydroxide solu- 
tion. The base and the acid are said to neutralize each other. 
6. Remove the litmus, and evaporate the solution over a 
flame until crystals begin to appear. Then let the solution 
evaporate further by itself. What is the shape of the crystals? 
Taste the crystals and the solution. What substance is formed 
by the neutralization of sodium hydroxide by hydrochloric 
acid? 

c. Take about 5 cu. cm. of filtered lemon juice, add a small 
piece of litmus paper, and neutralize the solution with lime- 
water. Remove the litmus, and boil the solution vigorously. 
You should get a white precipitate of calcium citrate. Give 
your results. 

d. On a piece of black or blue woolen cloth put a drop of 
concentrated hydrochloric acid, and let it remain for a few 
minutes. What happens? Now treat the acid spot with dilute 
ammonia water. What is the result? How could you remove 
an acid spot from cloth? 

Make another spot on the cloth; then apply a thin paste of 
baking soda (sodium bicarbonate). Will this do as well as 
ammonia water? 

EXERCISE 67 
SOAP AND SOAP MAKING 

Apparatus and Materials. Olive oil, sodium hydroxide solution, 
solid sodium hydroxide, "tin" can, lard, salt, blotting paper or news- 
paper, red litmus paper, linseed oil, limewater, test tubes. 

a. In a test tube put about 2 cu. cm. of sodium hydroxide 
solution and 1 or 2 drops of olive oil. Close the test tube with 



70 LABORATORY EXERCISES 

your thumb or a cork, and shake it vigorously. What becomes 
of the oil? Half fill the test tube with water, and shake it 
again. Do you get a good suds? The oil and the alkali react 
to give a soap. 

b. Dissolve 5 g. of sodium hydroxide in 35 g. of water, and 
put the solution in a clean "tin" can. Add 2 g. of lard; then 
carefully heat the mixture to boiling. Place a loose cover over 
the can, and do not allow the alkali to be spattered into your 
eyes. 

Boil the mixture for about 20 minutes; then add to it 10 
g. of salt in 3 portions. Stir the contents of the can, but 
do not look into it! After the salt is all in, boil the mixture for 
10 minutes more; then let it cool thoroughly. The soap should 
separate out as a solid cake that floats upon the solution. 
Take it out, rinse it with water, and lay it on blotting paper or 
newspaper to dry. 

c. Put a small piece of the soap you have made into a test 
tube, and shake it with some water. Does it make a good 
suds? Review Exercise 30, 6. 

Test the soap solution with red litmus paper. Is there a 
strong alkaline reaction, or not? 

d. Shake together in a closed test tube about Ve of a test 
tube full of linseed oil and half a test tube full of limewater. 
What is the appearance of the mixture? Do the materials 
separate easily when allowed to stand? What is an emulsion? 
See 91, text. 

EXERCISE 68 
TESTING OF COTTON AND WOOL 

Apparatus and Materials. Glass or porcelain dishes, 10 per cent 
sodium hydroxide solution, white cotton cloth and thread, white 
woolen yarn, dilute sulphuric acid, mixed cloth, burner, beaker or 



DYEING 71 

a. Soak a piece of new, white cotton cloth for 5 minutes in a 
10 per cent solution of sodium hydroxide. Then take out the 
cotton, wash it free from the alkali, and dry it. Has the cotton 
been changed in any way? Treat a piece of white cotton 
thread in the same way; is the thread noticeably weaker, or 
not? What is the mercerizing process? See 227, text. 

6. Test the strength required to oreak a piece of white 
woolen yarn. Now soak it for 5 minutes in a 10 per cent 
sodium hydroxide solution, rinse out the alkali, and again test 
the strength of the yarn. Result? Do you think that a 
"strong" soap, that is, one containing much alkali, would be 
good for woolens? 

c. Soak a piece of white cotton cloth in dilute sulphuric acid 
for 5 minutes. Dry it without rinsing; then rub it between 
your hands. What becomes of it? Do the same to a piece of 
white wool (flannel or yarn). Is it affected like the cotton? 

d. Get a piece of mixed cloth, that is, one consisting of both 
cotton and wool. Soak it in dilute sulphuric acid, and dry it 
without rinsing. Rub it between the hands; what falls out? 
Which material is this? 

e. Take another piece of the mixed cloth, and boil it for 
5 minutes (Care ! Do not let the alkali spatter into your eyes !) 
in a beaker or "tin" can with 10 cu. cm. of 10 per cent sodium 
hydroxide. This takes out the wool. What happens to the 
cloth's appearance? Rinse out the alkali, and dry the cotton. 
If you wished to get the exact proportion, by weight, of cotton 
and wool in a cloth, how would you proceed? 



EXERCISE 69 
DYEING 

Apparatus and Materials. Bottle or flask; beakers or dishes of 
porcelain or enameled ware; solutions of alum, lead acetate ("sugar of 



72 LABORATORY EXERCISES 

lead"), and potassium dichromate; new, unbleached cotton cloth; 
white woolen yarn; cochineal (powdered) and picric acid. If the dyes 
are furnished in solution, less material will be wasted. 

a. Into a bottle or flask put about half a teaspoonful of 
powdered cochineal and 100 cu. cm. of water. Shake the 
mixture from time to time during 10 minutes; then let it settle. 

Prepare a mordant of aluminum acetate as follows : 

To half a test tube full of lead acetate solution in a beaker or bottle 
add about 10 cu. cm. of alum solution. A white precipitate of lead 
sulphate is formed at once. Let this settle, and add more of the alum 
solution (about 1 cu. cm. at a time) until no more precipitate is formed. 
Let the precipitate settle completely; then pour the clear solution of 
aluminum acetate into another dish. Throw away the white pre- 
cipitate. 

b. From a piece of new, unbleached cotton cloth cut off 
5 strips about 2.5 cm. (1 in.) wide and 10 cm. (4 in.) long. 
Wash the strips with soap and water, and rinse them. 

Put 50 cu. cm. of the cochineal solution into a beaker or 
porcelain dish, heat it to gentle boiling, and leave a strip of the 
cotton cloth in it for 2 minutes. Remove the cloth, rinse it 
thoroughly, and let it dry. Is the color fast? 

c. Soak the second piece of cloth in the aluminum acetate 
solution for 2 minutes, remove it, and let it dry for 5 minutes. 
Then boil it in the cochineal solution for 2 minutes. Remove 
the dyed cloth, rinse it thoroughly, and dry it. Is the color 
fast now, or not? Paste the cloth in your note book, and label 
it. Save the mordant for e. 

d. Dissolve about 2 grams of picric acid in 20 cu. cm. of hot 
water; add 3 drops of dilute sulphuric acid. Put into the hot 
solution a piece of white woolen yarn and a strip of the cotton 
cloth. Heat the solution to boiling for 2 minutes; then remove 
the cloth and the yarn, and rinse them thoroughly. Which 
one is dyed permanently? Its color? 



BLEACHING 73 

e. Soak a piece of the cotton cloth in the mordant of a; let 
it dry for 5 minutes; then boil it in the picric acid solution for 
2 minutes. Rinse the cloth, and let it dry. Is the color fast 
now? Which material is dyed directly by picric acid? Which 
indirectly f 

/. Boil a piece of the washed cotton cloth in a solution of 
sugar of lead (5 cu. cm.) ; then leave it for 2 minutes in a boiling 
solution of potassium dichromate. Rinse the cloth, and let it 
dry. What is the result? 

Paste all the dyed materials in your note book, giving them 
the proper labels. 

EXERCISE 70 
BLEACHING 

Apparatus and Materials. Bleaching powder, hydrochloric acid, 
colored cheesecloth or mosquito netting, unbleached muslin, ink, glass 
or porcelain dishes (beakers or cups). 

a. Make a bleaching solution out of about 5 cu. cm. (a tea- 
spoonful) of bleaching powder (chloride of lime) and 100 cu. cm. 
of water. Stir this for 5 minutes; then either filter it or pour 
off the clear solution. Note the odor of bleaching powder and 
of its solution. 

Get ready also some rather dilute hydrochloric acid (5 cu. 
cm. of concentrated acid and 50 cu. cm. of water). 

6. Into the bleaching powder solution put a small piece of 
cheap, colored cheesecloth or mosquito netting (use pink, green, 
or blue, if possible) . Let it remain in the solution for 2 minutes, 
and note whether the color is altered. Now take the colored 
material out of the bleaching powder solution and dip it into the 
dilute hydrochloric acid. How does this affect the color? If 
the color is still unchanged, try dipping the cloth once more into 
the first solution and leaving it a longer time before you put it 
into the dilute hydrochloric acid. Give the results. 



74 LABORATORY EXERCISES 

c. Get a piece of new, unbleached muslin. What is its 
color? Why has it a color? Try to remove the color by means 
of bleaching powder solution and dilute hydrochloric acid, as 
you used these in b. Finally rinse the muslin thoroughly, and 
let it dry. What is the result? 

d. Make an ink spot on a piece of white muslin. Try to re- 
move the spot by soaking it first in bleaching powder solution and 
then in dilute hydrochloric acid. What are "ink eradicators"? 

Would it be a good plan to try to remove ink from a colored 
fabric by means of bleaching powder solution and dilute 
hydrochloric acid? Tell why. 

EXERCISE 71 
HOW TO REMOVE STAINS 

Apparatus and Materials. Piece of black cloth, candle or lard, 
benzine or gasoline, blotting paper, white cloth, rusty iron, hydro- 
chloric acid, white paint, grass or leaf, alcohol. 

a. Make a spot, with candle grease or lard, on a piece of 
black goods. Remove it by putting a few drops of benzine or 
gasoline on the spot and rubbing it with a black cloth. A piece 
of clean blotting paper or a pad of cloth may be placed under the 
spot to absorb the liquid and the grease it has dissolved. Try 
the operation more than once, if necessary. 

6. Rub a white cloth with a rusty can or nail until you get a 
decided stain. You can get a still deeper stain by putting a 
drop of ferrous sulphate (copperas) solution on the cloth and 
letting it dry. Soak the stain in dilute hydrochloric acid (5 cu. 
cm. of concentrated acid to 50 cu. cm. of water) for about 5 
minutes; then rinse it thoroughly with water. If the stain is 
not removed, try a second time. 

In the household, lemon juice and salt are used to remove 
rust stains. This mixture acts like dilute hydrochloric acid. 



PLUMBING 75 

c. With white paint make a small spot on some black goods. 
To remove the paint spot soak it in a teaspoonf ul of gasoline or 
benzine. These liquids dissolve the linseed oil of the paint 
(cf. 229, text). Let the cloth dry; then brush off the white 
powder that remains. What is the powder? 

d. With grass or some other green plant make a stain on 
white muslin. Soak the stain in a little alcohol, and rub the 
spot with a clean white cloth. Result? 



EXERCISE 72 
PLUMBING 

Apparatus and Materials. Sample or demonstration faucets, 
plumbing trap, piece of old lead pipe or trap. 

a. Examine Fig. 28. If you were closing the "compression" 
faucet, would the water pressure in the pipe help to close the 





Fia. 28 

The faucet on the left is a Compression faucet, the one on the right, a Fuller faucet. 
Both are cut open so that we can see how they work. Courtesy of the Central Scientific 
Company, Chicago. 

faucet, or would you have to overcome the water pressure? 
Which would be the case with the "Fuller" faucet? What simple 
machines are used in the opening and closing of these two faucets? 



76 LABORATORY EXERCISES 

If there is no sample faucet at school, get some one at home, 
or a plumber, to take a faucet apart for you and to show you 
how it works. Which of the two in the figure does it resemble? 
When a faucet leaks, so that you cannot cut off the water, what 
part is usually out of order? Which is the more likely to get 
out of order, the cold-water faucet or the hot-water one? 
Why? 

6. Examine a "trap." Make a drawing showing how the 
trap would look if cut lengthwise. Is the trap like that shown 
in Fig. 200, 236, of the text? If not, how does it differ? 

If a trap is stopped up, how should you clean it? How does 
a trap form a "water seal"? Why is a water seal necessary? 
Suppose that strings and hair collect in a trap, so that they 
extend over the bend shown on the right of Fig. 200 (the text) , 
would they be likely, or not, to carry away the water of the 
trap? See Fig. 25, 32, text. Why should such materials not 
be allowed to accumulate in a trap? 

c. Examine an old piece of lead pipe, such as an old trap. 
Is there any evidence of its having been worn thin? What 
wore it thin? If grease is deposited in a trap attached to a 
kitchen sink, what could be used to "cut" the grease? Why 
should the cutting substance not be left standing in a lead 
trap for a long time? 

EXERCISE 73 

FLAMES 

Apparatus and Materials. Iron spoon, burner, candle, glass tube 
about 10 cm. long, kerosene lamp, matches; materials for an alcohol 
lamp, if needed (see e). 

a. Hold an iron spoon in the luminous flame of a burner or 
candle. What happens? Where does the soot come from? 
What is soot? 



FLAMES 



77 



Hold the sooty spoon in a colorless Bunsen flame. What 
happens? Why? What substance is present in excess in the 
luminous flame? In the non-luminous Bunsen flame? 

b. Take a piece of glass tubing about 10 cm. (4 in.) long, and 
hold it at an angle of about 45 degrees, with the lower end of the 
tube in the central part of a large candle flame. Apply a lighted 
match at the upper end of the tube. Can you get a gas to burn 
there? Try the same experiment with a luminous gas flame. 
Are the gases in the central part of the candle and gas flames 
burning? 

c. After a candle has been burning for some time, blow out 
the flame. At once apply a lighted match above the wick 
but not touching it. Can you relight the candle? Try the 
experiment again to find out how far from the wick you can 
hold the match and still relight the flame. How does this 
experiment show that a candle flame is 

really a burning gas? 

If possible, try the same experiment 
with a kerosene lamp. Results? Why 
does a kerosene lamp give off such a 
strong odor after you have blown out the 
flame? 

d. In the center of a luminous gas 
flame hold the head of a match. Does 
the head take fire? What does this show 
as to the interior of the gas flame? Try 

the same experiment with a large candle FiG 29 

flame. 

e. An alcohol lamp can be made, if you need one, out of 
an empty library-paste jar (Fig. 29). You can buy a round 
wick, or you can make one out of calking twine or darning 
cotton. 




78 LABORATORY EXERCISES 

EXERCISE 74 
GAS AND ELECTRIC METERS 

Apparatus. Home meters for gas and electricity, fuse box. 

a. On the left half of a page of your note book make 5 neat 
pencil copies of the gas meter shown in Fig. 212, 256, of the 
text. Do not, however, put in the "hands" of the meters until 
they are called for. On your first drawing put in the hands 
just as you find them on your home meter. If the upper circle 
of your meter is intended to read only to 2 cu. ft., change your 
drawings accordingly. On the right half of the page, opposite 
the first meter, write down in figures the reading of the meter 
and the date on which the reading was made. 

6. Exactly one week after the first reading take a second 
one, putting in the hands of your second drawing. Opposite 
the drawing put in the date, the reading, and the difference 
between the first and second readings. Continue making the 
readings for 4 weeks. 

What was the total gas consumption for the 4 weeks? 
What was the average for a week? What was the cost of the 
gas for the 4 weeks? 

c. Find the key or lever by which the gas supply can be cut 
off so that it cannot go through the meter. How could you 
prevent gas from escaping if a pipe should burst somewhere in 
the house? 

d. In the same way as in a, but on another page, draw 5 copies 
of the kilowatt-hour meter. See Fig. 215, 259, of the text. 
Take 5 readings, just a week apart, and mark the positions of the 
hands on the dials. Date each drawing, write down the readings 
in figures, and give the differences between successive readings. 

How much electric energy did your family use each week? 
What was the total? The average for a week? What was the 
total cost? 



THE DEW POINT 79 

e. Examine the fuse box in your house, and tell how it is 
constructed. Find out how you could cut off the current 
entirely if you wished to. 

EXERCISE 75 

HOW HEATING THE AIR CHANGES ITS DENSITY 

Apparatus and Materials. Balances, flask holding about 100 to 
200 cu. cm., string, weights or shot, Bunsen burner. 

a. By means of a string having a loop at one end suspend a 
clean, dry flask from one arm of a balance. Into the pan 
attached to the other arm put weights or shot, enough to bal- 
ance the flask. Now remove the flask and heat it by turning 
it rapidly in a Bunsen flame; then put it back in its place on the 
balance. What is the result? 

Let the flask hang until it becomes cool ; what happens? What 
evidence have you that hot air is lighter, that is, has a lower 
density, than cool air? 

EXERCISE 76 
THE DEW POINT 

Apparatus and Materials. Metal beaker or bright metal (aluminum 
or tin) cup, thermometer, large bottle with small mouth, bits of ice. 

a. Use a simple dew-point apparatus, such as is shown in 
Fig. 217, 267, of the text. The metal beaker may be a bright 
aluminum or tin cup. Have the cup % full of water at the room 
temperature; then add bits of ice or snow, stirring vigorously 
with the thermometer until the first drops of dew are deposited 
on the cup. Now get the thermometer reading at once, and 
record it. To repeat the trial take out any ice that remains, 
and let the water become just warm enough to permit the dew 
to evaporate. Then add another bit of ice, and stir with the 



80 LABORATORY EXERCISES 

thermometer until dew is deposited. Get the thermometer 
reading; is it the same as before? 

b. If air is saturated with water vapor, and we lower its 
temperature, even slightly, we cause a fog to be formed. One 
way by which we can cool air is to cause it to expand. The 
experiment is carried out by pouring water in spurts (cf. 
Exercise 1) from a large bottle that has a small mouth. Half 
fill such a bottle with water, and invert it over a pail or sink. 
Notice that as a spurt of water falls out, and the air inside is 
slightly expanded, a cloud or fog is formed, but that as soon as 
an air bubble enters, and the air in the bottle is again at the 
ordinary pressure, the fog disappears. 

How does this experiment explain the formation of clouds in 
rising currents of air? 

EXERCISE 77 
WEATHER RECORDS 

Apparatus and Materials. Weather reports, or thermometer, 
barometer, rain gauge, and weather vane; if possible, an anemometer. 

a. Keep a weather record for at least two weeks, putting 
down your observations under the heads given below. For 
the temperature you can use your home thermometer or the 
one at school. For the barometer height inquire each day at 
school, or get it from the daily weather report in your local 
newspaper. You will need to depend on some one with a rain 
gauge, or on the weather report, for the amount of precipitation; 
you yourself can tell whether it is rain or snow. 

You can also tell the direction of the wind. Judge of its 
velocity according to the table given in 274 of the text. 
Describe the clouds as in 269 of the text. Make your own 
readings, twice a day if possible: first in the forenoon, and again 
in the afternoon. 



KINDS OF ROCKS 



81 



Date 


Hour 


Temper- 
ature 


Barome- 
ter Height 


Direction 
of Wind 


Velocity 
of Wind 


Kind of 
Clouds 


Amt. of 
Precipita- 
tion 


Rain or 
Snow 





























































































EXERCISE 78 
WEATHER MAPS 

Material. Weather map. 

a. Get a weather map from the Weather Bureau. Paste it 
in your note book. What is the lowest pressure shown on the 
map? The highest? Where are the "lows" of the map, that 
is, in what states? The "highs"? 

b. What is the difference in pressure, in inches, between two 
successive isobars (lines of equal pressure)? What happens 
when the isobars are close together? See 274 of the text. 

Are there any lines of equal temperature (isotherms) on the 
map? For what temperatures are they given? Why are they 
so irregular? 

EXERCISE 79 
KINDS OF ROCKS 

Apparatus and Materials. Pocket knife, cent, triangular steel file; 
the substances named in a; hydrochloric acid. 

a. Examine a piece of each of the following materials : sand- 
stone, marble, limestone, rock salt, soft coal, hard coal, shale, 
conglomerate, quartz, feldspar, granite, glass, soapstone, slate, 
brick, pumice, concrete, gypsum. 



82 



LABORATORY EXERCISES 



What is the color of each? Is the material all of one color, 
or of different colors? Which substances are crystalline? 
See 69 of text. "Heft" each substance to determine whether 
it is dense or light. 

b. Try to scratch each substance, with 

1. Your finger nail. 

2. A cent piece. 

3. A knife blade. 

4. A triangular steel file. 

Which of the substances scratch glass? 

c. On the surface of each piece put a drop of hydrochloric 
acid (1 cu. cm. of the concentrated acid to 3 cu. cm. of water). 
Do any of them effervesce; that is, get frothy and give off tiny 
bubbles of gas? 

How can you distinguish rock salt from all the others? 

d. Classify your results under the following heads: 



Material 


Color 


Crystalline 
or not 


Dense or 
Light 


Hard or 
Soft 


Does it React 
with Acid? 











































































EXERCISE 80 
CONCRETE 

Apparatus and Materials. Tin can (tomato can), measuring cup, 
wooden paddle or iron spoon, block for "tamp," pasteboard box 
(small), cement, sand, and gravel. 



ORE TESTS 83 

a. Measure out J4 of a cupful of fresh, powdered cement, ^ 
of a cupful of fine, sharp sand, and a cupful of rather fine gravel 
(stones about Y^ the size of a coffee bean). Do the mixing 
in a quart tin can (tomato can) ; for the stirring use a wooden 
paddle or an iron spoon. First put in the sand; then add 
the cement, and stir the two together. Wet the gravel, and 
mix it with the sand and cement, adding water little by little, 
so as to form a thick, "mushy" mixture. Finally pack the 
mixture (use a block for a "tamp") into a small pasteboard 
box; have the top of the mixture just below the top of the 
box. 

b. Make a finishing coat for the concrete out of about l /& of a 
cupful of cement and J4 of a cupful of fine sand. Put these into 
the empty can, mix them with enough water to form a paste, 
and spread the paste evenly over the concrete. Use a flat 
block or a kitchen knife for a trowel. 

Cover the concrete loosely with paper, and set it aside for 
3 or 4 days to harden. Note its appearance from day to day. 
What is its color when hard? Finally remove the cover, expose 
the concrete to the light, and wet its surface once or twice a 
day. What is the effect of this treatment upon the color of 
the concrete? 

c. What advantage has concrete over flagstones for use in 
sidewalks? Over bricks? What is reinforced concrete? 

The mixture described in a is called a 1, 2, 4 mixture; why? 



EXERCISE 81 
ORE TESTS 

Apparatus and Materials. Pieces of pyrite (iron pyrites), hematite, 
galena, and copper ore; -magnet or magnetized knife blade; piece of 
charcoal or of soft earthenware, such as a piece of a flower pot; mouth 
blowpipe; Bunsen burner or alcohol lamp. 



84 



LABORATORY EXERCISES 




NOTE. Dr. J. C. Foye, in his " Handbook of Mineralogy/' tells 
how to make a home-made mouth blowpipe out of a clay pipe (Fig. 
30, this manual). His method is given in modified form. A piece of 
pipe stem about 5 cm. (2 in.) long is broken off, 
and the hole in the smaller end is filled for a dis- 
tance of about 1 cm. with putty. A fine needle 
is pushed through the putty. The closed end of 
the pipe stem is heated in a Bunsen flame until 
the putty is hard; the needle is then pulled out. 
There remains a small, smooth hole. 

The piece of pipe stem is fastened to the bowl 
of the pipe by means of plaster of Paris. Cut 
out of cardboard a circle that will just go into 
the bowl of the pipe, make a hole in the center, 
and push the piece of pipe stem through the hole. 
Push the cardboard into the bowl, having the 
prepared "tip" outward, and fill the bowl, above 
the cardboard, with a thick paste of plaster of 
Paris and water. When the plaster of Paris has 
"set," the blowpipe is ready for use. 

a. Test the pieces of pyrite and hematite with a magnet. 
Are they attracted? 

b. Break a small piece of pyrite into powder, and heat it on 
charcoal, or on a piece of soft earthenware, in a blowpipe flame. 
The method is as follows: 

With a pocket knife hollow out a depression near one end of the 
piece of charcoal, and put the powdered pyrite into it. To make the 
blowpipe flame we use a luminous gas flame about 4 cm. (1.5 in.) high. 
Hold the charcoal in your left hand, and the blowpipe in your right. 
Place the tip of the blowpipe just at the outer edge of the flame at its 
middle part, and blow a steady stream of air against the flame. Have 
the tip turned slightly downward, so that the flame produced will be 
forced down upon the pyrite. Hold the pyrite so that it will be at 
about the middle of the long blowpipe flame. In using the blowpipe, 
breathe regularly through your nostrils; your puffed-out cheeks should 



FIG. 30 

AHome-Made Mouth 
Blowpipe. 



ORE TESTS 85 

serve as bellows. Do not blow in jerky breaths. With a little 
practice you will be able to produce a steady, hot flame. 

You can use the blowpipe with an alcohol lamp, if you have no gas. 
Put into the alcohol y io of its volume of turpentine. 

c. After you have heated the pyrite for a minute, smell of it. 
Can you perceive the odor of burning sulphur? What element 
must pyrite contain? 

Continue heating the pyrite for several minutes in the blow- 
pipe flame; then let it cool, and test it with a magnet. Is it 
attracted? What element, besides sulphur, is present in 
pyrite? Read 137, text. 

d. Rub some hematite on white paper; what color has its 
"streak"? 

Heat powdered hematite in the blowpipe flame, as you did 
pyrite. Is any odor of burning sulphur given off? Is the 
material that remains magnetic? What metal is present in 
hematite? 

e. Examine a piece of galena and describe it. Break off 
some pieces; what shape do they seem to have? 

Heat powdered galena on charcoal in the blowpipe flame, as 
you did pyrite. Do you get the odor of burning sulphur? 
Heat the galena steadily for some minutes; what happens? 
Let the product cool and try to cut it with a pocket knife. 
What substance is it? What elements are present in galena? 

/. What is the color of the copper ore? Break off a little, 
powder it, and mix it with an equal volume of 'dry washing 
soda. Heat the mixture in the blowpipe flame. Cut out the 
mass on the charcoal, break it up finely, and put it into a white 
dish. With water wash away the excess of soda, charcoal, and 
unchanged ore. Do you find any heavy material that looks 
like copper? 



86 LABORATORY EXERCISES 

EXERCISE 82 
KINDS OF SOIL 

Apparatus and Materials. Drinking glasses or bottles, teaspoon, 
gravel, sand, clay, and black loam. 

a. Get samples of 4 kinds of soil : gravel, sand, clay, and loam. 
Get as dark a loam as possible. 

Crush each sample of soil with your hands, and rub it between 
the tips of your fingers. Which is made up of the largest 
particles? Which of the smallest? 

b. Wet a teaspoonful of each kind of soil; then work it be- 
tween the fingers. Which soil sticks together best? Which 
crumbles most easily? 

c. Put a heaping teaspoonful of the gravel into a drinking 
glass half-full of water. Stir the water thoroughly, let it settle 
one minute, then pour off the liquid into another dish. To the 
gravel that remains in the glass add as much water as you 
poured off, and stir the water again. Let the liquid settle 
for one minute; then pour off the water. Write down your 
results. 

d. Treat each of the other kinds of soil with water, as you did 
the gravel, and record all the results. 

Does much or little material settle out from the water 
that is poured off? Which soil settles least in the minute 
given it? Which most? Describe the materials left after 
the second stirring with water. 



EXERCISE 83 
SOIL TESTS 

Apparatus and Materials. Black loam, white sand, filter paper, 
funnel, porcelain or "tin" evaporating dish, burner, beaker or flask, 
test tube, dilute hydrochloric acid, 2 saucers, thermometer. 



HOW SOILS TAKE UP THE RAIN 87 

a. Soluble Matter in Soil. Get a filter paper and a funnel 
ready for use (see 84, text). Nearly fill the filter paper with 
black loam, packing the soil in as tightly as you can. Pour 
through the soil 100 cu. cm. of boiling water, about 5 cu. cm. 
(a teaspoonful) at a time. Catch the filtrate, and evaporate it 
in a clean porcelain or tin dish over a can of boiling water. 
Describe the material that remains after evaporation. 

6. Organic Matter in Soil. Put into your iron dish the soil 
that is left in the funnel, and heat the dish. Heat gently at 
first, so as to dry the soil; finally heat it as hot as you can. 
Note how the color of the soil is changed by the heating. What 
caused the dark color? Why does it disappear? 

c. Put a teaspoonful of fresh loam into a beaker or flask, 
shake or stir it up with about 50 cu. cm. of water, and pour 
off the turbid liquid. Do this twice more. To the soil that 
remains add a test tube full of dilute hydrochloric acid. Boil 
the mixture gently for about 10 minutes. 

What is the appearance of the substance that is left? What 
is the advantage of having this substance in soil? Can you 
suggest what materials may have been taken out of the soil by 
means of the hydrochloric acid? See 217, text. 

d. Soil Absorbs Heat. Fill one saucer with dark, black loam 
and another with white sand. Make sure that the two have 
the same temperature; then expose them both to bright sun- 
light. After 10 minutes take the temperature of each. Is one 
warmer than the other? Which one? Why? 



EXERCISE 84 
HOW SOILS TAKE UP THE RAIN 

Apparatus and Materials. Vinegar or ketchup bottle with bottom 
removed, fruit jar, measuring cup, Bunsen burner, piece of muslin, 
string, gravel, sand, loam, and clay; watch or clock. 



LABORATORY EXERCISES 



Soil 



a. Prepare a bottle and a fruit jar as shown in Fig. 31, this 
manual. One way to break off the bottom of the bottle is to 
drop a metal rod, such as a solid metal curtain rod or a straight 
poker, through the mouth of the bottle. An- 
other way is to hold the bottle horizontal and 
rotate it over a small, but hot, Bunsen flame, 
so that it will be heated in a circle parallel to 
the bottom. Then plunge the bottle into cold 
water; the bottom will usually break off. Close 
the mouth of the bottle by tying a piece of 
muslin over it. 

6. Tie a string tightly around the bottle, 
about 5 cm. (2 in.) from the broken end. This 
serves as a mark. Fill the bottle to the mark 
with small gravel. Shake the material, and 
ffl B) press it down, but do not make it too compact. 

Then set the bottle in the fruit jar. 

Pour upon the gravel just a cupful of water. 
Do not add the water all at once, but pour it 
upon the upper surface just as fast as the 
gravel can absorb it. Note the time when 
you add the first water; then find out just how long it takes 
for the water to begin to drip from the mouth of the bottle. 

c. Empty out the gravel, and fill the bottle to the same mark 
with fine sand. Add the cupful of water as before, and take the 
time. 

d. Repeat the experiment of b with loam; then with clay. 
Give all the results? What causes the difference in results? 

Which soil allows water to pass through it most rapidly? 
Which least rapidly? Which soil would be the most likely to 
have water standing on it after a rain? Which would be the 
least likely? 



FIG. 31 



HOW MOISTURE IS TAKEN UP BY PLANTS 89 

EXERCISE 85 
CONTENTS OF A FERTILE SOIL 

Apparatus and Materials. Three one-quart flower pots, clay, sand, 
garden soil (loam), ammonium nitrate, potassium chloride, powdered 
rock phosphate or bone meal, 3 glass covers, oats. 

a. Into each of 3 one-quart flower pots put a layer of clay 
2.5 cm. (1 in.) deep. Fill the first pot with good garden soil, 
the second with clean sand; for the third make the following 
mixture: a scant pot full of clean sand, half a teaspoonful of 
ammonium nitrate, 24 of a teaspoonful of potassium chloride, 
a tablespoonful of powdered rock phosphate or bone meal. 
Mix these materials thoroughly, and fill the third pot with the 
mixture. Label the third pot. 

b. Provide each flower pot with a glass cover. Soak some 
oats over night (not longer) in water; then plant 16 of the 
soaked seeds in each pot, about M of an inch below the surface. 
Put down the date of planting. 

Cover the pots with the glass covers, and set them in diffused 
light (not direct sunlight) in a warm room. Keep the soil moist 
but not soggy. Note how long it takes for the seeds to sprout 
(record the date) ; then remove the covers, set the young 
plants in the sunlight, and watch their growth from day to 
day for several weeks. 

c. Do all the seeds sprout? In which pot do the seedlings grow 
most rapidly? What necessary plant food is supplied by each of 
the 3 materials mixed with the sand of the third pot? Does 
garden soil contain these plant foods? 

EXERCISE 86 
HOW MOISTURE IS TAKEN UP BY PLANTS 

Apparatus and Materials. Egg, napkin ring or wide-mouth bottle, 
glass tubing 7 cm. long, candle, iron wire (thick hair pin), hat pin, egg 



90 



LABORATORY EXERCISES 



cup or small glass, small potted plant (see e), glass tube, rubber tube or 
adhesive tape. 

a. In this exercise we are to study the phenomenon called 
osmosis, or the passing (diffusion) of water and dilute solutions 
through thin membranes. In this way the dilute soil solution 
enters the root hairs of the plant. We can study osmosis most 
easily by the use of an egg (Fig. 32). 

Tap the large end of an egg so as to crack the 
shell; then pick off the shell, bit by bit, from an 
area about as large as a cent. Be very careful 
not to break the thin membrane ("skin") inside 
the shell. Crack the small end also, but do 
not remove the shell from an area more than 
1 or 2 mm. in diameter. Stand the egg in a 
napkin ring, or in the mouth of a bottle, so that 
the smaller end is upright. 

b. Select a piece of glass tubing about 7 cm. 
(3 in.) long. From one end of a candle cut off, 
by means of a hot piece of iron wire (a thick hair 
pin will do), a round piece about 6 mm. (J^ of 
an inch) thick. Take out the wick, and with 
the heated wire enlarge the wick hole so that 
the glass tubing can just be pushed in. Use the iron wire 
(reheat it when necessary) as a "soldering iron" to fasten the 
edge of the wax securely to the glass. See that the opening 
of the glass tube is not closed with wax. 

Now hold the glass tube so that the piece of wax is against 
the small end of the egg, and so that the hole in the glass tube 
is just over the opening in the shell. With the heated wire 
melt some of the wax, and fasten the lower edge of the wax 
securely against the egg shell. 

c. Push a hat pin through the glass tube, and thus break the 
skin in the small end of the egg. Put the egg in an egg cup or 




FIG. 32 



PLANTS GIVE OFF MOISTURE 



91 




small glass (Fig. 32) , adding water enough to rise a third of the 
height of the egg. Then set the apparatus aside, and examine 
it from time to time. Observe it after an hour 
or two, if possible. 

d. What do you observe in the glass tube? 
How does this show that water passes through 
the skin at the larger end of the egg? If 
water were free to enter through ordinary 
holes in the skin of the egg, would anything 
rise into the glass tube? 

e. A small potted plant, such as a geranium, 
or some plant out of doors, may be cut off 
about 5 cm. above the ground, and a glass tube 
may be fastened to it by means of a rubber 
tube or by adhesive tape (Fig. 33, this manual). 
The glass tube should be filled with water to 
the top of the tape or rubber. If the plant is 
kept watered, sap will rise into the glass tube. 

If possible, try the experiment, and 
note how high the liquid will go. 

EXERCISE 87 
PLANTS GIVE OFF MOISTURE 

Apparatus and Materials. Plant, card- 
board, knife or shears, paraffin (white 
wax), cloth or brush, large tumbler or 
fruit jar. 

a. Select a thrifty plant, such as 
a geranium, growing in a pot, and 
water it thoroughly (Fig. 34). Cut 

out a piece of cardboard larger than the top of the pot; 

in it make a round hole that will just fit the stem of the 



Fio. 33 




FIG. 34 



92 



LABORATORY EXERCISES 



plant. Also cut a slit from the edge of the cardboard to the 
central hole. 

Use a piece of cloth, or a small brush, to "paint" the card- 
board with melted paraffin, so that it will be water-tight ; 
then slip the cardboard around the stem of the plant and over 
the pot. Close the slit in the cardboard with melted wax, 
and pack some of the soft, but not hot, wax around the stem. 

b. Over the plant put a large tumbler or a glass fruit j ar, and set 
the plant in bright sunlight. Look at the jar from time to time. 
Can you see a deposit of water inside it? What part of the plant 
gives off the water? Why does a potted plant need to be watered 
frequently? 

EXERCISE 88 
SEEDS AND THEIR GERMINATION 

Apparatus and Materials. Germination box, or "flat," good soil, 
pocket knife, garden beans, lima beans, scarlet runner beans, castor 

beans, squash seeds, 
peas, corn, radish seeds, 
red clover seeds, some 



other seeds. 

a. Make a germina- 
tion box like that 
shown in Fig. 35. The 
box should be about 
10 cm. (4 in.) deep, 50 
cm. (20 in.) wide, and 
60 cm. (24 in.) long, all 
inside measure. The 
squares will then be 5 
cm. (2 in.) on a side. 
The squares are marked off by thread held in place by tacks 
that are driven into the sides of the box. The figures may be 



FIG. 35 



SEEDS AND THEIR GERMINATION 93 

made, in ink, on the edges of the box. In the figure, square 
No. 1 is in the lower right-hand corner; No. 10 is in the upper, 
right-hand corner; No. 120 is in the upper, left-hand corner. 
Fill the box with good garden soil (loam) ; pack it down gently. 

b. Soak in water over night (not longer) 14 garden beans, 14 
lima beans, 14 scarlet runner beans, 14 castor beans, 14 squash 
seeds, 14 peas, and 14 grains of corn. Plant one seed in each 
square, in a hole made with a small stick (pencil), and about 
1 in. deep. Put 12 beans in the first (lower) row of holes, 12 
lima beans in the second row, and so on. Save the 2 remaining 
soaked seeds of each kind for e. Label each row of seeds 
carefully, giving the date of planting. 

In row 8 from the bottom plant 12 radish seeds; in row 9, 
12 red clover seeds; in row 10 any seeds you wish. 

Water the soil moderately, but do not soak it. Keep the box 
in a sunny window of a warm room. Now proceed with e. 

c. After 2 or 3 days, begin to excavate carefully around the 
seeds in squares 1 to 10 (the first vertical row on the right- 
hand side). If any of the seeds have germinated, take them 
out and examine them carefully. Study 307 and 308, text. 

You will need to keep a careful record. For this purpose 
rule two opposite pages of your note book, together, into 120 
squares like those of the germination box. In each square 
make note of the time when you examined the seed in the 
square, and the condition of each seed part; that is, the testa, 
cotyledons, plumule, and hypocotyl. 

d. After the seeds of each kind begin to germinate, remove 
one each day for 6 days, or until each seedling has grown 
definitely out of the ground. Leave the remaining seedlings to 
grow more fully. Observe them every day, and save them 
for further study in Exercises 90, 91, and 93. 

In which of the plants that have 2 large cotyledons do the 
cotyledons come above ground? In which do they become 



94 LABORATORY EXERCISES 

green? In which do they remain attached? Describe all the 
changes that the cotyledons undergo. Why do they change? 

e. Examine the soaked seeds of b that were not planted. 
How is the testa of each affected by the soaking? Look for 
the scar (hilum) showing the place at which the seed was 
attached. With a knife cut through the testa; do it carefully, 
so as not to mutilate the plumule or the hypocotyl. In the 
beans you can cut on the curved edge. Pick off the testa, 
and spread the cotyledons apart. Describe what you find in 
each case. 

In the corn look for the single cotyledon. After removing 
the testa cut through the kernel lengthwise, at right angles 
with the flat surfaces. Describe all you find. 

EXERCISE 89 
MATERIALS PRESENT IN PLANTS 

Apparatus and Materials. Scissors or a knife, bottle, saucer or 
evaporating dish, iron dish, glass cover, burner, test tube, white 
writing paper, grass or other green leaves, alcohol, slaked lime or 
soda-lime, flour, starch, iodine solution, corn meal, potato, radish, lard 
or linseed oil, benzine, ground flax seed. 

a. Chlorophyll. With scissors or a knife cut up very finely 
a handful of grass, spinach, parsley, or other green leaves. If 
you have a mortar and pestle, you can crush the material also. 
Put the material into a bottle, and cover it with alcohol. Let 
the bottle stand, stoppered, for an hour or two, and note the 
colored solution that is produced. 

Pour out a few cubic centimeters of the solution into a 
saucer, and let the alcohol evaporate without heating it. 
Note the green chlorophyll that remains. If you wished to 
prepare a green "ice," how could you get a harmless coloring 
material? 



MATERIALS PRESENT IN PLANTS 95 

b. Nitrogen. Thoroughly mix about a test tube full of fine 
grass cuttings with half a test tube full of slaked lime. Soda- 
lime is still better; use it if you can. Put the mixture into 
your iron dish. Cover the dish with a clean piece of glass on 
the under side of which you have pasted a piece of wet, red 
litmus paper. Heat the dish carefully; does the litmus change 
color? If so, ammonia is being given off. Can you get its 
odor? If ammonia is given off, the grass must contain nitrogen 
(cf. 112, text). 

Try the same test with flour instead of with grass. Use 
equal volumes of flour and lime (or soda-lime). What are the 
results? Does flour contain nitrogen? 

c. Starch. Cook a pinch of laundry starch with half a 
test tube full of water. Pour the liquid out into a white saucer 
or evaporating dish to cool; then add a drop of iodine solution 
(a small crystal of iodine dissolved in 5 cu. cm. of a dilute 
solution of potassium iodide). What happens? This is a test 
for starch. 

Try the experiment with a pinch of flour instead of starch. 
Try it again with corn meal; also with scrapings from the freshly 
cut surface of a potato. Try it with the scrapings from a 
radish, parsnip, or sweet potato. Give all the results. 

d. Fat. Put a speck of lard or linseed oil on a piece of clean, 
white writing paper; then wipe off the lard or oil, and hold the 
paper between you and the light. What do you see? 

Put a drop of benzine on the paper, and hold the paper to 
the light. Does benzine produce a permanent stain on the 
paper? 

Put a small heap of corn meal on the paper and wet the meal 
with benzine. After 3 or 4 minutes remove the meal, and let 
the benzine evaporate. Is there a stain? Do the same with 
ground flax seed. Result? Is fat present in the seeds of corn 
and of flax? 



96 



LABORATORY EXERCISES 



EXERCISE 90 
STUDY OF LEAVES 

Apparatus and Materials. Different kinds of leaves, 2-quart and 
1-quart glass fruit jars, bottle, marble, dilute hydrochloric acid, pan 
and pail of water, parsley or spinach, test tube, pine splinter. 

a. Get together at least 15 kinds of leaves in addition to 
those on the seedlings of Exercise 88. Get leaves of trees and 
weeds as well as of garden plants; be sure to know the name 
of the plant to which each leaf belongs. Include in your list, 
if possible, the leaf of the apple tree, of red and white clover, 
of the maple, and of the black locust. 

Study 309, of the text, for some of the differences between 
leaves. Do any of the leaves you have brought have stipules? 
Have all of them petioles? Which leaves are deeply indented? 
Which ones are compound, that is, broken into leaflets? What 
is the kind of veining in each leaf? 

Have you found any plants with tendrils? If possible, get 
a leaf of Boston ivy and some of the suckers by which it clings. 

b. Classify the facts learned in a under the following heads: 



Name of 
Leaf 


Simple or 
Compound 


How In- 
dented 


Has It 

Stipules? 


Petiole? 


Color and 
Shade 


Veining 


Shape 



































































































c. The Work of Leaves. Half fill a 2-quart fruit jar with 
water, and hold over the mouth of it a bottle in which you are 
generating carbon dioxide from marble and dilute hydro- 



STEMS 97 

chloric acid (see Exercise 40). Pour the gas into the fruit jar, 
but do not pour over any of the liquid (see Exercise 15). From 
time to time close the mouth of the fruit jar with your hand, 
or with the cover belonging to the jar, and shake the jar vigor- 
ously, so as to make the gas dissolve in the water. 

Fill a quart fruit jar (see Fig. 235, 310, text) loosely with pars- 
ley or spinach; then add the carbon dioxide water to overflowing. 
Invert the jar (do not let any air bubbles enter) in a pan of the 
carbon dioxide water. Let the bottle stand in bright sunlight 
for two days, if possible. Do gas bubbles collect over the water? 

Transfer the gas, under water (see Fig. 78, 102, of text), 
to a test tube filled with water and inverted in the water. If 
the gas does not fill the test tube, close the mouth of the test 
tube, under water, with your thumb; then remove the test 
tube and invert it. Test the gas with a glowing splinter. 
What is the gas? What change did the leaves bring about? 

EXERCISE 91 
STEMS 

Apparatus and Materials. Pocket knife, pocket magnifier; young 
twig and older stem of lilac, box elder, oak, poplar, cherry, elm; corn- 
stalk, handle of palm leaf fan or a palm leaf; a potato, also one that 
has sprouted in the dark; rhubarb stalk; red ink. 

a. Read 312, 313, 314, and 315, text. Examine the young 
twig and an older stem of a lilac. Describe the color and appear- 
ance of the bark. Look for marks of any kind. Where are the 
nodes? Can you find the scars of leaves of other years? How 
are they arranged? How are the buds related to the leaf scars? 
Do the buds go singly, or in pairs? How is one set of buds 
arranged with respect to the next set? Is it directly above it? 

Cut across a bud, and describe what you see. Has your 
twig a growing tip? Describe it. 



98 LABORATORY EXERCISES 

b. Make a smooth cut across the young twig and the older 
stem. If you need to saw the stem, polish the sawed surface 
with fine sandpaper, so that you can see the markings plainly. 
Also cut a small piece of the lilac twig lengthwise. 

Examine the cut surfaces carefully; if possible, use a mag- 
nifier (cf. Exercise 51, c). Compare the cross section of the 
lilac stem with Fig. 238, a, of the text. Are the two exactly 
alike? Identify the epidermis, cortex, woody bundles, and pith. 
Also find the pith rays and annual rings. 

c. Study a young twig and an older branch of the box 
elder as you did the lilac. What resemblances? What differ- 
ences? 

Do the same with one of the following : oak, poplar, cherry, 
or elm. 

d. Examine a piece of a last year's cornstalk; it should con- 
tain a node. Cut off the end smoothly, and examine the cross 
section. Does the cornstalk have its materials arranged in 
concentric circles, as the other stems have? Note that the 
interior is pith, with woody (fibre-vascular) bundles scattered 
through it. Draw a cross-sectional view of it. 

Cut the cornstalk lengthwise, so that you can follow the 
course of some of these bundles. 

If possible, cut or saw across the handle of a palm leaf fan, or 
of a palm leaf itself. Does the cross section resemble the corn, 
or the lilac? 

e. Examine a potato that is sprouting, or ready to sprout. 
Find the "eyes." What evidence is there that the scales are 
imperfect leaves? Do the potato buds arise in the axils of the 
leaves? How much of the potato must be planted in order 
that a new potato plant may be formed? 

Note the color of the leaves of a potato that has sprouted 
in the dark; why are they so? Bring the potato into bright 
sunlight for a few hours; what change takes place? 



WOOD 99 

/. Cut off a small slice from one end of a potato, and set 
the potato with its cut end in a shallow dish (saucer) containing 
water. After an hour color the water with red ink, and allow 
the potato to remain in the dish for 3 or 4 hours. Finally cut 
the potato open lengthwise. How high has the red color 
risen? Has it risen through the whole of the potato, or along 
certain lines? What are these lines? 

Cut off slices (cross sections) from the potato, beginning at 
the end that was farthest from the colored water. What 
evidence do you get that the water rose into the potato? 

g. Carry out the same experiment as in /, using a stalk of 
rhubarb with the leaf attached. First cut off a piece from the 
lower edge of the stalk. Can you see the ends of the woody 
bundles? Now put the stalk, first, into water, then into 
colored water, and leave it some hours, or over night. Cut 
off slices from the stalk at various places. What is the appear- 
ance of the ends of the woody bundles? See if the colored 
water has gone into the leaf. Is the rhubarb a monocotyl or 
a dicotyl? 

You can use the weeds plantain, burdock, and lamb's- 
quarters as well as rhubarb for this experiment. 

EXERCISE 92 
WOOD 

Apparatus and Materials. Sandpaper, carpenter's plane (?), "tin" 
can; several kinds of wood, wire nail, hammer, paint, shellac, burnt 
umber, linseed oil, turpentine, a cloth, and a paint brush. 

a. With sandpaper smooth the surfaces of blocks or boards 
of oak (plain-sawed and quarter-sawed), whitewood, white 
pine, Georgia pine, and hemlock. If the ends are rough, 
smooth them first with a plane (or have a carpenter do it); 
then use the sandpaper. 



100 LABORATORY EXERCISES 

Describe the appearance of the ends, faces, and edges of each 
block or board. How do the two kinds of oak differ in appear- 
ance? 

Try to drive a wire nail into each of the boards, about 1 cm. 
(half an inch) from the end; which kinds split most easily? 
Suggest why. 

b. Get a smooth piece of Georgia pine, or of yellow pine, that 
has a knot passing through it. Describe the appearance of 
the knot and of the wood around it. Wh,at is a knot? 

Paint one side of the board, both the knot and the wood 
around it. Cover the knot on the other side of the board 
with shellac; after a few minutes paint over both the knot and 
the wood. Let the paint dry thoroughly for a day or two; 
then examine the two sides of the board. What is the differ- 
ence in their appearance? Is there any good reason why 
knots in a board should be covered with shellac before 
painting it? 

c. Put a piece of knotty yellow pine or hemlock in hot sun- 
light or near a hot radiator or stove. What happens to the 
knots? Describe the odor produced; what causes it? 

d. Make some brown stain by mixing ^ of a teaspoonful 
of burnt umber with 2 teaspoonfuls of linseed oil, and then 
adding about % of a cupful of turpentine. The materials 
may be mixed in a "tin" can; the stain should be kept in a 
stoppered bottle. 

Apply the stain with a cloth or brush to one face and the 
smoothed end of each of your blocks of wood. Let the stain 
remain on the wood for 5 minutes; then wipe it off with a cloth. 
After the stain has entirely dried, examine the blocks. Which 
were stained most deeply, the ends, or the faces, of the blocks? 
Tell why. Which kind of wood "took" the stain best? Why? 

N. B. Be sure to burn the oily cloths, or to put them into 
a covered metal can, so that they cannot set the building afire. 



THE FLOWER JjJ J 101 



EXERCISE 93 
ROOTS 



Apparatus and Materials. Garden trowel, the germination box of 
Exercise 88, glasses of water, dandelion, sweet potato, dahlia roots, 
turnip, parsnip, carrot, onion. 

a. Read 316 of the text. Carefully loosen the soil around 
a young radish in the germination box, and take out the plant 
without injuring its roots. Note how the root hairs cling to 
the particles of soil. Why do they? 

Put the root into a glass of water, and note the multitude of 
root hairs. Make a drawing of the entire plant. 

b. To which of the two classes of primary roots do the roots 
of radishes belong? Carefully dig up a grass plant, place the 
roots in water, and wash off the soil. To which class do the 
roots of grass belong? Make a sketch of them. 

In the same way examine, describe, and sketch the roots of 
the bean, pea, squash, clover, and corn seedlings. 

c. Dig up a dandelion; \o which class does its root belong? 
Examine the root of a dahlia; to which class does it belong? 
How does it differ from the root of the grass? 

d. How do you know that a sweet potato is a root, while an 
ordinary potato is a modified stem? 

If possible, examine the roots of the turnip, parsnip, and 
carrot. To what class of roots do they belong? Is an onion a 
root? Prove your answer. 

e. Give 3 important uses of roots. 

EXERCISE 94 
THE FLOWER 

Materials. A simple flower, also clover and dandelions. The 
kind of simple flower will depend somewhat on the season and the 
location of the school. Among wild flowers the trillium, spring beauty, 



102 LABORATORY EXERCISES 

hepatica, dog( tooth violet, anemone, and wild rose are excellent 
material. The blossoms of the apple, cherry, pear, plum, and straw- 
berry may be used. The Easter lily is excellent because of its size. 
The clover illustrates flowers that grow in a "head"; the dandelion is 
an example of composite flowers. 

a. Read carefully 318 and 319 of the text; then examine 
the flower in hand. Has it a distinct stalk? Is the stalk thick 
or slender? Rough or smooth? Is it tough, or easily broken? 

6. Has the flower a calyx? Its color? Is the calyx made 
up of separate parts, or are they united? What are these parts 
called? How many are there? 

Examine the receptacle; has it any special shape or color? 

c. Describe the corolla, giving its color, markings, number 
of parts, and the shape of the parts. What are the parts of 
the corolla called? Are they alike in all respects? 

d. Describe the stamens, giving their number, color, shape, 
and arrangement. Describe the filament; the anther. Is 
there pollen? 

Do the stamens grow directly on the receptacle, or are they 
attached to the corolla or other plant organ? Are all the 
stamens of the same length? 

e. Examine the pistil of the flower; what is its shape and 
color? What is the form of the style? How many carpels are 
there in the pistil? How many stigmas are there? 

What is the form of the ovary? Cut across the ovary at 
the top and at the thickest part. Describe and draw what you 
see. How many compartments are there in the ovary? Cut 
lengthwise through the ovary; how are the ovules attached? 

/. Is the flower you are studying built on the plan of 3, or 
of 5 parts? What kind of veining has the leaf of the plant? 
Compare this flower with others, note resemblances and differ- 
ences. Can you find any connection between the kind of vein- 
ing of the leaf and the number of parts of the flower? 



THE EARTHWORM 103 

g. Examine a "head" of clover, with the magnifying glass if 
possible; of what is the head composed? Remove an in- 
dividual blossom by cutting it off at its point of attachment. 
Take the blossom to pieces, and describe the flower parts in 
detail. Which part of the clover head matures first, the outer 
or the inner part? 

h. Study the dandelion. Note that it is made up of many 
flowers growing on the same receptacle. Describe the corolla 
of each flower. Describe the stamens and pistil. 

Examine a dandelion that has gone to seed. Remove the 
winged seeds (akenes), and describe one of them. Make a 
drawing of one. Draw the receptacle that remains. Describe 
the double circle of green "leaves" below the receptacle; are 
they true leaves? Are they sepals? 

EXERCISE 95 
THE EARTHWORM 

Materials. Earthworm and leech. 

a. Read 336 of the text. Put an earthworm on a moist sheet 
of paper (newspaper), or on some moist earth, and find out how 
it crawls along. Which is the anterior (head) end? Does the 
worm crawl forward or backward? While it is moving, touch 
the part that is forward; does the worm reverse its direction? 

Count the number of segments in the earthworm. Count 
the number in several specimens, if possible. Do all have the 
same number? 

b. Look carefully at the worm while it is at rest. Can you 
see any pulsations, or "beats," that pass through the body? 
What are these? Is the body wall of the worm thick or thin? 
Do any of the internal organs show through the body wall? 

c. Does the earthworm require air for its respiration? Why 
are so many worms found on the ground and sidewalks after 



104 LABORATORY EXERCISES 

a heavy rain? In the morning look for the tracks of earth- 
worms; describe them. Find also the holes leading to the 
earthworm burrows; account for the heaps of earth about them. 
How does the earthworm go through the ground? What 
effect does it have upon the soil? 

d. If the laboratory has a leech, examine its movements. 
Compare the leech with the earthworm. 

EXERCISE 96 
MOLLUSKS 

Materials. Shell (both halves) of the freshwater clam (mussel), of 
the saltwater clam, of the oyster; a snail shell; if possible, a living clam 
and a living snail. An oyster "on the half shell" will also be useful. 

a. Study 337 of the text. Examine the clam shell and the 
oyster shell; compare the two. 

Describe the appearance of the outside of the clam shell. 
Which part of the shell was the top (dorsal part) and which the 
bottom (ventral part) in the living animal? Are the two 
halves of the clam shell exactly alike? 

If you have a living clam, find which is the anterior (head) 
end; then find which is the right valve and which the left valve 
of the shell. Draw an outside view of the left valve, showing 
the markings and the hinge. Trace the outside markings all 
the way around the shell. Label the parts of the drawing. 

6. Describe the inside of the clam shell; then draw the inside 
view of the left half, showing the markings as accurately as pos- 
sible. Why does the presence of these marks indicate that the 
shell increases in size? Which part of the shell is tfye oldest? 

c. Examine the insides of both halves of the shell for the spots 
at which the two muscles (anterior adductor and posterior ad- 
ductor) were attached (see Fig. 261, text). Can you see any 
evidence that a spot may not always have been at the same place? 



INSECTS 105 

d. Examine the hinge, and note the tough ligament that held 
the halves of the shell together. Which act required muscular 
effort on the part of the animal, to close the shell, or to open it? 
Can you find on the hinge the device by which the shell was 
thrown open? If the projecting material at the hinge forms the 
fulcrum, if the stretching of the ligament represents the work to 
be done, and if the contraction of the muscles is the power, what 
kind of a lever is the shell when the clam is trying to close it? 

If you were trying to pry the shell open, and the clam were 
trying to keep it shut, to what other class of levers would the 
shell belong? Where would the power be as regards the ful- 
crum and the new resistance? To exert the greatest force, 
ought the muscles to be attached near the hinge or near the 
ventral edge of the shell? Where are they attached? Why? 

e. If you have a clam or oyster identify the cut ends of the 
muscles, also the mantle, foot, and "siphons." 

/. Carefully examine a snail shell; sketch an outside view of 
it. If possible, get some one to saw lengthwise through an 
empty shell, from the tip to the widest part. Draw a section 
of the shell. In what part did the animal live first? 

g. Describe the body and movements of a living snail. 



EXERCISE 97 
INSECTS 

Materials. House fly and horsefly, spider, ant, May beetle; if 
possible, a butterfly or a moth; also a spider's web, the larva of a May 
beetle (" white grub"), and a cocoon of the cecropia moth. 

A convenient way to catch a butterfly or moth is to use a bag of 
mosquito netting attached to a ring and pole; for the other insects use 
a wide mouth bottle. Put this over the insect; then slip a piece of 
cardboard between the mouth of the bottle and the table or wall on 
which the insect had alighted. 



106 LABORATORY EXERCISES 

a. Read 339 of the text. Answer the following questions 
for each insect you can study : 

1. How many regions has the body? Are they equally 
distinct in all the insects examined? 

2. How many pairs of legs has the insect? To which region 
of the body are they attached? What ones are put forward 
at the same time? 

3. How many pairs of wings has the insect? Are all of them 
used for flying? To what body region are they attached? 
What are the markings of the wings? 

4. How many segments are there in the abdomen? Are all 
the segments of the same shape and size? Are any structures 
attached to these segments? 

5. What is the shape of the head? What parts of the head 
can you distinguish? What is the shape and size of the parts 
of the mouth? How are they used? What does the insect eat? 

6. Can you find the eyes of the insect? How many are there? 
What is there remarkable about the eyes of insects such as the fly? 

b. By digging in a barnyard or in a strawberry patch, or 
even in the open field, you can usually find " white grubs," the 
larvae of the May beetle. Examine one carefully, and describe 
it. What is its color? Can you count its body segments? 
Has it "feet?" To what parts are they attached? Describe 
the parts of its mouth. What does the grub feed upon? 

c. If possible, find a spider's web; study its construction, 
and draw it. Are the webs of all spiders alike? Out of what 
do spiders spin webs? Why do they spin webs? 

d. Between late fall and early spring you will usually be 
able to find the large, dense cocoons of the cecropia moth. 
They are brown, and attached to the branches of such trees 
and shrubs as the apple, cherry, willow, lilac, maple, and 
elder. Get several, if possible, and put them into a box with a 
cover of wire netting. 



BIRDS 107 

Often the cocoon is empty. You can tell, by "hefting" the 
cocoon, whether there is a pupa inside or not. If there is, 
cut open the cocoon, beginning at the open end. Use slender, 
sharp scissors, and be very careful not to injure the creature 
inside. Touch the pupa; result? Sketch it. 

When you are through examining the pupa, see that it is placed 
as it was when you opened the cocoon, and close the slit with a 
strip of gummed paper; then lay the cocoon in the net covered 
box. Leave the box where it will be warm, and where the sun- 
light will shine on the cocoon. You may be rewarded, in the 
spring, by the appearance of the beautiful imago, the adult moth. 

e. Look for some ants; you will usually find them on side- 
walks or along the road. Follow them, and find out where they 
live. Carefully open up their "house," and see the galleries 
they have formed. Tell what they do when disturbed. 

EXERCISE 98 
BIRDS 

Materials. Skeleton of bird, live chicken, foot and leg bones of a 
duck, leg bones and wing bones of a chicken and a turkey, feathers of 
a chicken, duck, pigeon, goose, and turkey; a chicken gizzard. 

a. Read 344 of text. If the school has the skeleton of a bird, 
study it carefully, and compare its bones with those of Fig. 269. 

6. Examine the foot of a domestic fowl ("chicken"), noting 
the scales. How many toes has the chicken's foot. How many 
are directed forward? How many backward? Is the chicken 
a perching or a climbing bird? Find the end of the white 
tendon that is connected with the chicken's toes, and pull it. 
What happens? 

If possible, examine the foot of a duck. How does it differ 
from that of a chicken? Has this difference anything to do 
with the habits of the two birds? 



108 LABORATORY EXERCISES 

c. What is the scientific name of the chicken bone that we 
commonly call the "drumstick"? See Fig. 269. What is the 
bone of the "second joint"? Compare these with the corre- 
sponding bones in the human skeleton. See Fig. 275, 354, 
text. What bones are in the foot of the bird? If possible, 
study the leg bones of a duck and a turkey, and compare them 
with those of a chicken. 

Compare the bones of a bird's wing with those of your own 
arm and hand. What bones of the wing bear the feathers 
most needed for flight? Do these correspond to the bones of 
the upper arm, lower arm, or hand? 

d. Get a large wing feather, also a small contour feather, or 
body feather, of the chicken, duck, pigeon, goose, and turkey. 
Examine the quill of each feather, and describe it. Is it hollow 
or solid? Is the axis, or central part, hollow all the way? 

The outspread part of the feather is called the vane. The 
parallel rows that make up the vane are the barbs. Which 
feathers have the barbs joined together? Which ones have 
them separate? Which class of birds would need to have 
the barbs joined, flying birds or walking birds? Why? 

e. Examine the eye of a living chicken; how many eyelids 
has it? The extra one is the nictitating membrane; in what 
direction is it moved across the eye? 

/. At home or in the meat market have a chicken gizzard cut 
open for you. What materials do you find inside it? Why 
does the fowl eat such things? Note the tough, rough, inside 
covering. What is its use? Note the thick muscular walls; 
why are they needed? Why does a bird need no teeth? 

g. Are any birds harmful to man? Give examples. Do 
these birds make up in any way for the harm they do? Why 
is it important that a farmer should know the birds on his 
farm, and their habits? Send for Farmers' Bulletin No. 630, 
U. S. Department of Agriculture, Washington. 



BONES AND JOINTS 109 

EXERCISE 99 
BONES AND JOINTS 

Apparatus and Materials. Pocket knife or needle mounted in a 
small stick (dissecting needle), beef or mutton bone containing a joint 
and sawed lengthwise, an old bone, chicken bones, a slender bone, 
such as a " wishbone" or the rib of a lamb chop. 

a. Read 352, 353, and 354. Examine the bone in a piece 
of uncooked "round" steak. Ask the butcher to get you a 
fresh, long, beef (or mutton) bone that contains a joint end. 
Have him saw the bone lengthwise, for an inch or two, through 
the joint; then have him cut off one of the lengthwise pieces. 

Examine the sides and ends of the bone. What kind of 
material covers the bone? Name it. Identify the marrow. 
Can you find marrow of two different colors? At what part of 
the bone is each kind? Do you find cartilaginous material at 
the j oint? What are its uses? Describe the interior of the bone. 

6. Compare with the new bone an old bone that has been 
dried thoroughly, or has lain out of doors for some time. 

c. Collect the bones of a fowl ("chicken") after the flesh 
has been removed, and clean them thoroughly. Test some of 
the bones to determine whether they are hard, or easy, to 
break. Are they at all elastic? Chop, or saw, lengthwise into 
the leg bone ("drumstick"); is it solid, or hollow? 

Find a hinge joint in the chicken; a ball-and-socket joint. 

d. Thoroughly clean and dry a slender bone, such as the 
"wishbone" of a chicken or the rib of a lamb chop. Boil it 
for a few minutes in water; then let it soak in hydrochloric 
acid (1 volume of concentrated acid to 4 volumes of water) for 
3 or 4 days. Finally rinse off the acid and examine the bone. 
Is it hard now? What has the acid removed? 

e. Burn a small bone in a place where there is a good draught, 
or on a bed of hot coals. Continue heating it until it is white. 



110 LABORATORY EXERCISES 

Let the bone cool; then examine it. Is the burnt bone tough, 
or brittle? What did the burning remove from it? 

EXERCISE 100 
MUSCLES AND TENDONS 

Apparatus and Materials. Pocket knife or dissecting needle (see 
Exercise 99) ; tough, lean beef and tender beef; tendon from a sheep's 
hoof, a heavy book, magnifying glass (?). 

a. Read 355 and 356 of the text. Ask the butcher for 
a small piece of lean beef that is sure to be tough. From what 
part of the animal does it come? Ask also for a small piece 
of tender beef. Cut across the muscle fibers of each, and ex^ 
amine the cut ends. Is there any difference in their appear- 
ance? Use a magnifying glass if possible. 

Cook the tough piece until the fibers can be picked apart 
(not cut) with a knife or needle. What is the name of the 
tissue between them? Why was the piece tough? 

6. Recall the appearance of the tendon in the chicken's foot 
(Exercise 98). Ask the butcher to get for you the tendon in 
the hoof of a sheep; describe it. 

c. Place one forearm on the table, with the elbow on the table 
and the palm upward. Let the arm and hand be relaxed (limp) . 
With the other hand find the tendon that attaches the biceps 
muscle to the radius of the lower arm (see Fig. 277 of text) . Note 
how it stiffens when you raise the forearm, especially if you 
have a considerable weight, such as a heavy book, in your hand. 

d. Repeat c, but feel of the biceps muscle in your upper arm 
instead of the tendon. How does it change? 

e. To what class of levers does the forearm belong? See 
Fig. 277. Would you need to exert more, or less, force to lift 
a flatiron that is in your hand than if it were attached just 
above your wrist? Why? 



FOODS AND FOOD TESTS 111 

EXERCISE 101 
FOODS AND FOOD TESTS 

Apparatus and Materials. Potato, kitchen grater, laundry starch, 
measuring cup, flour, cheesecloth, test tube or beaker, grape sugar, 
Fehling's solution (see Introduction), raisin, granulated sugar, hydro- 
chloric acid, white of egg, nitric acid, ammonia water, white woolen 
yarn, white cheese or sour milk, ground peanuts. 

a. Starch. Peel a potato, grate it fine, and stir it with water. 
The starch will thus be separated from the other material, 
such as cellulose, and will tend to settle to the bottom. If you 
then pour off the water and the lighter sediment, the starch 
will remain. Pour the starch upon a filter paper or a piece of 
newspaper, and let it dry. 

Note the "crunchy" feeling of some laundry starch when you 
crush it between your fingers. 

Boil about ^ of a teaspoonful of powdered starch in your 
measuring cup with J4 of a cupful of water. Let the mixture 
cool; it should "set" to a thick paste. Review Exercise 89, c. 

b. Gluten. Out of J^ of a cupful of flour and a little water 
make a tough dough. Tie the dough in a piece of good cheese- 
cloth, and knead the dough under water. Note that the 
starch comes through the cloth. When no more starch can be 
kneaded out of the dough, examine the impure gluten that 
remains. Give its color. Is it sticky? Elastic? 

c. Grape Sugar. Into a test tube or small beaker put a 
pinch of grape sugar; dissolve it in the least possible amount of 
hot water. Add to the solution about 3 cu. cm. of Fehling's 
solution, and boil the mixture. What is the result? This 
serves as a test for grape sugar. Taste a little of the grape sugar. 

Crush a raisin, soak it in water, and boil the solution with 
Fehling's solution. Is grape sugar present? 

Dissolve a pinch of granulated sugar in the least possible 
amount of water, and boil with Fehling's solution. Result? 



112 LABORATORY EXERCISES 

To another portion of a solution of granulated sugar add 1 
drop (not more) of concentrated hydrochloric acid. Boil the 
solution for a few minutes; then add Fehling's solution and boil 
again. Has the granulated sugar been changed to grape sugar? 

d. Proteids. In a beaker boil half a teaspoonful of white of 
egg with about a test tube full of water. Note how the pro- 
teid is coagulated. Pour off the water, and heat the white of 
egg with dilute nitric acid. How is its color changed? Now 
put the white of egg into ammonia water. Is the color removed, 
or made more intense? 

Boil a piece of white woolen yarn in the nitric acid in which 
you heated the white of egg; then put the yarn into ammonia 
water. Results? Do the same with a piece of white cheese, 
or with the curd of sour milk. Results? 

e. Fats. Review the test for fats in Exercise 89, d. Try it 
with some ground peanuts. 

EXERCISE 102 
THE MOUTH AND THE THROAT 

Apparatus. A hand mirror, a rubber band. 

a. Read 359, 360, and 361 of the text, also 388. Go 
through the process of chewing a rubber band, and make a 
note of all the motions of your tongue, teeth, jaws, cheeks, and 
the special organs of swallowing. Swallow the saliva and at 
the same time feel of your throat. What rises in it in the act 
of swallowing? You can understand these motions better if 
you stand with your back to a well-lighted window and look 
into a hand mirror. 

b. Open your mouth wide, and examine the inside by the 
aid of the mirror. Can you move any part of the roof of your 
mouth? This is the soft palate. Is it in the front, or the back, 
of the mouth? 



DIGESTION OF FOOD 113 

Describe the tongue; compare its upper and under surface. 

Swallow all the saliva you can, so as to get the mouth as 
free from it as possible; then raise your tongue, and note 
how the saliva gathers under it. Where does the saliva come 
from? 

c. Hold your tongue in the bottom of your mouth, and 
identify the tonsils at the side of the throat. 

d. Count the total number of teeth in each jaw, and the num- 
ber of each kind. How do the teeth differ? Why? 

EXERCISE 103 
DIGESTION OF FOOD 

Apparatus and Materials. Bottles or beakers, pan of water, litmus 
paper, corn starch, white bread, hard-boiled egg, grater, rennet (or 
junket tablet), milk, thermometer, pancreatin, pepsin (get the ferments 
at a drug store), olive oil, Fehling's solution. 

a. Saliva. Put into your mouth a piece of clean, pink 
litmus paper; what effect has the saliva upon it? Has saliva 
an acid, or an alkaline, reaction? 

Put on the tongue a pinch of powdered cornstarch; let it 
soak in the saliva, and note if it becomes sweet. How does 
saliva affect starch? 

Chew a piece of white bread; does it become sweet? 

b. Gastric Juice. Grate finely a part of the white of a 
hard-boiled egg ; put a teaspoonf ul of it into a bottle containing 
about 100 cu. cm. of water, a teaspoonful of dilute hydrochloric 
acid, and a good-sized pinch of pepsin. Also add a piece of the 
ungrated white of egg. 

Put the bottle in a warm place for several hours, or over 
night. What is the result in the case of the grated material? 
The larger piece? What is the reason for keeping the materials 
warm? What is the advantage of the chewing of food? 



114 LABORATORY EXERCISES 

c. Rennet. Into a bottle put about 50 cu. cm. of milk, and 
set the bottle in a dish of water at 37 to 38 C. (about 100 F.). 
Add some commercial rennet, or a " junket" tablet. Keep the 
milk warm for about 10 minutes; then set it aside. What hap- 
pens? Which part is curd? Whey? What does each contain? 

d. Pancreatic Juice. Dissolve a little commercial pan- 
creatin, or pancreas extract, in warm (not hot) water; divide 
the solution into two parts. Add half of the pancreatin solu- 
tion to a tablespoonf ul of olive oil and the sam6 volume of warm 
water. Set the mixture in a warm place. . Shake up the mix- 
ture from time to time for 2 or 3 days. Note what happens. 

Make a smooth starch paste by mixing a teaspoonful of 
starch with 3 or 4 teaspoonfuls of cold water. Set the paste 
in a pan of warm water, and add to it the other half of the 
pancreatin solution. Let it stand for at least a day, and note 
what happens. If possible, test the product with Fehling's 
solution? Has the starch been changed to sugar? 

EXERCISE 104 
THE BLOOD VESSELS 

Apparatus and Materials. String, stethoscope (get it from a physi- 
cian), heart of sheep or calf, with the connecting organs. 

a. Press with three fingers upon the artery in the wrist, 
and count your pulse beats. How many are there each min- 
ute? In the same way "take the pulse" of an old person, and 
of a young child. Compare the number of beats. 

Take some vigorous exercise, or breathe very deeply a num- 
ber of times; what is the effect upon your pulse? 

b. Find the large veins on the back of your hand. Press the 
blood out of one of them by pushing down hard with a finger of 
your other hand and at the same time moving the finger from 
the wrist toward the knuckle. Notice that blood does not 



RESPIRATION 115 

enter the vein from either direction; the finger prevents its 
flow toward the heart, while the valves in the vein prevent the 
flow in the opposite direction. Remove the finger; result? 

c. Wind a string tightly about a finger, and note what takes 
place. What vessels carry blood into the finger? What ones 
carry it out? Which of these is closed by the string? Why 
is it important that arteries should not be near the surface? 

d. Ask a physician to show you a stethoscope and the way it 
" works." With it study the heart-beat of some member of 
your family. What sounds does the heart make? 

e. From a butcher get the heart of a sheep or calf, with the 
lungs and trachea attached if possible. Examine the blood 
vessels connected with the heart. Study their position by the 
aid of Fig. 284, 375, of the text. Distinguish the arteries 
from the veins by the differences in thickness, strength, and 
elasticity. Distinguish the ventricles from the auricles. In 
what part of the heart are the ventricles? Why are their walls 
so thick? 

/. If your specimen of the heart has the lungs attached, 
examine them. Are they heavy or light? Are they of exactly 
the same shape? What is their color? What is the shape and 
structure of the trachea? What keeps it in shape? 

EXERCISE 105 
RESPIRATION 

Apparatus and Materials. Watch, measuring tape, 2-qt. fruit 
jar, deep pan of water, glass tube, graduated cylinder, small-mouth 
bottle with bottom removed (Ex. 84), touch paper. 

a. .Read 381 to 391, inclusive, of the text. For the test 
for the presence of carbon dioxide in exhaled air, recall Exercise 
15, b. Test for water in exhaled air by blowing the breath into 
a cold bottle or against a cold window pane. What happens? 



116 LABORATORY EXERCISES 

b. When ycfu are breathing quietly and regularly, count the 
number of inspirations in a minute, and record them. Find 
out the number for another person of your own age ; for a young 
child. Count your respirations after violent exercise. 

c. With a measuring tape get the distance around your 
chest. To do this, pass the tape across your back and just 
under your arm-pits; bring it together just over your breast 
bone. Now breathe very deeply, and get the chest measure. 
Finally exhale all the air you possibly can, and get your chest 
measure. What is the difference between the last two results? 
This represents your chest expansion. 

d. Find how many cubic centimeters of air you can expel: 
(1) from lungs that are normally full of air; (2) from lungs 
that are as full as you can make them. The apparatus 
needed is a 2-quart glass fruit-jar, a pan of water, and a tube, 
as in Fig. 37, 45, of the text. You will need to know the 
capacity of the jar and the volume of water left after each trial. 
Results? 

e. You can show by simple means how the action of the 
diaphragm aids in bringing air into the lungs and in expelling 
it from the lungs. You need a small-mouth bottle from which 
the bottom has been removed (see Exercise 84). This form of 
the apparatus is suggested in Walters' Physiology and Hygiene. 
Set the bottle, right side up, in water that is about half as deep 
as the bottle is tall. Let the level of the water represent the 
diaphragm. As you raise the bottle, the water level falls, and 
air rushes into the bottle's mouth. This represents an inspira- 
tion. As you lower the bottle, the water level rises, and air is 
expelled; this represents an expiration. The results are seen 
better if a piece of smoking " touch paper" is held over the 
mouth of the bottle. To make touch paper, soak strips of 
filter paper or blotting paper in a solution of potassium nitrate 
(saltpeter), and dry them. 



THE NERVOUS SYSTEM 117 

EXERCISE 106 
THE NERVOUS SYSTEM 

Apparatus and Materials. Model of brain (?), brain of calf or sheep, 
piece of spinal cord, pair of dividers. 

a. Read 399, 400, and 401, of the text. If your school has 
a model of the human brain, study it, and identify its parts. 

Ask your butcher to get for you the brain of a calf or sheep, 
and study its form and appearance. Have him also get a piece 
of the spinal cord; describe a cross-sectional view of it. 

A section of the spinal cord may be found in the proper cuts 
of sirloin of beef. Ask the butcher to show you one. 

6. With your finger feel for the nerve at the elbow (" crazy 
bone"); what sensation is produced? When you hit the crazy 
bone against a hard object, where do you feel the tingling 
sensation? Why? 

c. Cross your middle finger over your first finger, and hold a 
pencil between the crossed ends of the fingers. How many 
pencils do there seem to be? Why? 

d. Close your eyes, and have some one touch the skin of your 
neck, hands, finger tips, forehead, and forearm, with a pair of 
"dividers." The two points of the dividers should be varying 
distances apart; sometimes one point should be used, sometimes 
both points. Where do you find the skin very sensitive; that 
is, where can the two points be distinguished as two, even when 
they are only a very small distance apart? 

EXERCISE 107 
THE EYES 

Apparatus and Materials. White paper, light-pink paper, printed 
letters //g of an inch high, circle of red paper, model of the eye (?). 

a. Read 414 to 418, inclusive, of the text. On a piece of 
paper make two circles (entirely black) about J^ of an inch in 



118 LABORATORY EXERCISES 

diameter and 3 inches apart. Hold the paper at arm's length, 
shut the left eye, and fix the right eye upon the left spot. You 
should see both spots. 

Now bring the paper toward the eye; when it is about 8 
inches away, the right-hand spot will disappear, because its 
image falls on the blind spot of the eye. At less than this dis- 
tance the right-hand spot will reappear. 

b. On a piece of paper draw 2 circles each 3 inches in diam- 
eter. Have the outlines heavy. On one of the circles draw 
parallel vertical lines, all the same distance apart. On the 
other circle draw parallel horizontal lines. Pifl the paper to 
the wall, and look at it from some distance. Do the circles 
appear to be true circles? How is each distorted? 

Repeat the experiment, using two squares. Results? 

If a wall paper contains many vertical stripes, what is the 
effect upon the apparent height of the room? What is the 
effect of horizontal stripes? 

If a person wishes to appear slender, ought he to wear cloth- 
ing with vertical or with horizontal stripes? 

c. Out of a newspaper or an advertising circular cut several 
letters % of an inch high. Paste them upon a sheet of white 
paper, and pin the paper to the wall. Find out how far away 
you can stand and yet see every letter distinctly. Measure this 
distance and record it. 

Ask an elderly person to try this test; get the distance. Ask 
a near-sighted person to do it. What are the results? . 

d. Get a sheet of light-pink paper (tissue paper), and hold 
it before you. Now look steadily at a red circle in bright sun- 
light; then look quickly at the pink paper. What kind of a 
circle do you see on the paper? Tell why. 

e. If your school has a model of the eye, study it carefully, 
and make out its parts. Compare them with Fig. 300, text. 



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